This will be real quick. I went back and forth about buying this bag thinking about buying something cheaper and I am not saying you can't get a good bag for less, but this bag is so comfortable and light and packs down so small, that if your on the fence and have the dough, don't be. It is a solid purchase, glad I bought it.

I had originally purchased a Western Mountaineering 30 degree bag but returned it as it was rather small in the shoulders. That bag also seemed to sacrifice a lot in terms of durability to save on weight. The Marmot Hydrogen bag is the perfect balance between weight, compressibility, warmth and comfort. The long version still packs down to something just a bit larger than a nalgene, and the weight is negligible. I have plenty of room to roll around in it and it has already held up well in Buffalo, NY early spring, which is none too warm at times (temps around 35-40 F at night). I have the sense that this bag would do well even below the 30 F rating.

I've used a lot of bags meant for cool to warmer nights and this is by far the best I've seen.

This is an excellent 3+ season bag that is conservative in its listed temperature rating.

It comes with a heavy nylon stuff sack that is 6"x12". The stuff sack bottom is round. The bag easily stuffed into this sack, and compresses into a approximately a 6"x6"x6" cube. The 850+ fill power down lofts up quickly on its own, and it lofts up even faster if you climb in the bag. The bag's fabric, Pertex, feels good on one's skin and it is slippery smooth. This allows you to roll around and not take the bag with you. I have not weighed the bag. The manufacturer's listed weight is 21 oz. Mine weighs 23.35 oz.

My bag has a half zipper, although current models have a full. When fully zipped, it locks into place as Marmot claims. I have no problems getting into or out of the bag, despite there being only a half-zip. The zipper tape is stiff and keeps the wispy shell fabric from being caught in the zipper.

I have used the bag twice in temps below the listed bag rating of 30 degrees F. Both those nights (10 and 11 degrees F) I was wearing a base layer top and bottom, liner socks, thick wool socks, 100 weight micro fleece pants, a 200 weight fleece vest and a thin hat. I was using a Therm-a-rest Prolite 3 (1" thick) underneath me. Both nights I was in a tent.

I have also used the bag on multiple nights in the mid 30's and lower 40's. Each time I slept in just a base layer and a thin fleece hat. I had either a Therm-a-rest Prolite 3 (1" thick) or a 57" Ridgerest underneath me. I was toasty warm. I would recommend this bag to a friend.

For going light in the summer/early fall this is a great bag. The interior liner of the bag is extremely comfortable and feels great against the skin. Although, this is a great sleeping bag for a specific situation, I would not recommend this bag if it is your only one. If you only plan to own only one bag, go with something a bit more substantial however, for warm weather light packing, this bag is about as good as it gets.

This is by far the best bag I have ever owned. I used to sleep in Marmot's Never Winter bag and that was a great bag no doubt, but once I made the switch it is incredible. This bag lofts to outrageous proportions and stuffs down so tiny. I think mine is an earlier model and weighs in at 1 lb. more than this and I thought that was light! I am only 5'10" and about 175 pounds, but I bought the long. My preferred method is to have my sleeping pad inside my bag inside a hammock to prevent it from moving around and is the reason why I chose a Long. I would only recommend that to people with my sleep method, otherwise stick to the regular sized bag. Marmot has supplied enough room to move around at will with the regular sizing(I move a lot at night and the Long was a must for me). Buy this bag and you will never look back....unless its to get the Helium bag by Marmot!

Best bag I've ever owned and I've been at this since 1965. I've used it in the Idaho backcountry this summer and fall and found its comfort range to be between 20 and 65 degrees. Above 60 you're pretty much on top with any bag. Below 20 if you add socks and long johns this bag can work at 10. Quality is excellent. Compresses to an amazing 5" X 8" and weighs nexst to nothing.

My husband and I both got new bags this summer. We love them. They are great for backcountry trips in the Sierras when you're also carrying climbing gear and need to cut weight where ever you can. Can't think of one negative(unless you don't look good in green).

I have about 6 sleeping bags and this is my favorite. I take it to the desert year round, spring/summer/fall trips in the mountains, hut trips in winter and in my car as an emergency bag in winter. Sleep comfortably at 30 and have used it on colder nights wearing clothes without trouble sleeping. I'm 6'0 and fit into the regular. Long would give a little more wiggle room and width but I like the smaller size and lighter weight of the regular. This bag has been stuffed and unstuffed countless times and still has tons of loft. Marmot is the only company that certifies fill power and the quality shows on the Helium. Full zip is key on an ultralight. Best ultralight bag out there.

Great bag, very light, warm for the weight. I'm 6' and sleep on my side and went with a long to get enough width for my knees.

this thing is amazing got used to the half zip in no time and couldn't be happier with it in my pack. i actually slept in it all winter squatting in a NYC loft without heat. and it still has all the down and lofts up like new after 4 years

I got lucky getting this as a gift, so I didn't have to worry about the price. It seems to me, though, that you can get a pretty crappy bag for 200, and this is well worth the extra investment. Incredibly comfortable and warm for its weight. Just wanted to add my satisfaction to the others'. I'll never get another bag.

Used this bag when I hiked the AT. Used it from Hot Spring to Damascus and then again from Vermont through Maine. It works as it should. Worth all the praise and the big $$ tag if hiking light is important. For me it is a must have and I will use it again in 2010. Tried and true!! Just make the extra effort to keep it dry.

This big fits neatly into my superlight niche for backpacking. Size and weight are almost nonexistent. I found the bag too warm on nights >50 degrees, but the full length zipper allowed it to be opened up and used like a blanket. I have not tested the bottom end of the temperature range but I feel comfortable that it could easily work to 20 degrees with a solid base layer or bivy sack. However, its greatest strength is also its greatest drawback in that down requires much TLC in any non-dry environment.

People: You won't be dissapointed if you buy the Marmot Hydrogen 30 Degree Down Sleeping Bag, it's so damn comfy that I burned my crappy REI sleeping bag last night...I can't believe the difference, it's the most comfortable sleeping bag I've ever had for backpacking...the last 3 trips have been an absolute pleasure, it packs smaller & lighter then my old bag, more shoulder room, more leg room, makes a great pillow for naps, & it's a Marmot bag (& they are known as the best bags in the outdoor industry)...so take that!!! The extra $ is worth it, just take care of it. :) I don't get cold that easy (usually 2 dogs & hopefully a girl in their with me), but it was 35 degrees when I took a temperature reading & I didn't need to mummy up at all, in fact I had my arms out of the bag...I'm pretty core though, so step off son!

I just received my bag in the mail, haven't use it yet. It was miss leading when indicated :Draft Collar-Insulated draft tube, I thought there was a draft tube inside, but it is just outside around where your face is.

I'm 6'2" and have plenty of room in the long. Slept comfortably down to the temperature rating, weighs almost nothing and packs down to the size of a loaf of bread. Great summer backpacking bag.

This bag is very small, light and toasty down to the mid 40s. I haven't used it at the 30 degree rating yet, but I should have the opportunity in a couple of weeks. It's also very roomy, which I like.