I have never been able to sleep comfortably in mummy bags - I get too claustrophobic and my arms cramp up, forcing me to alternate between cold arms out of the bag and cramped arms in the bag : (
So I set out to find a roomier bag, and had heard this was a BA specialty. I'm a 5'4 chick, and most roomy bags I'd seen were regular or men's cut. When I spotted the BA Roxy Ann in petite cut on Backcountry for a sweet discount, I hoped and prayed that this would be my bag.....
Tried it out for the first time in Death Valley this weekend, and it was the most comfortable night of sleep I have EVER had on the trail. This bag is indeed huge - I tend to sleep in the "Captain Morgan" position or curled up in a ball - you can get into pretty much any position in this bag.
That being said, the biggest downside to ultra-roomy bags like BA's is they are just not as warm - when you move, you will feel cold spots. They warm up pretty quickly in this 15 degree bag, but it could wake you up if you're a light sleeper. Now I am a cold sleeper to begin with, and with a silk liner, I was definitely not sweating as expected in overnight temps in the 40's. But, you could always add a fleece liner or layer clothes in sub-freezing temps - to me, it's a tradeoff for getting this much freedom of movement. My feet typically get the coldest, and the petite cut of this bag prevents excess dead air around your feet if your short - my feet stayed pretty toasty.
Weight is good for a bag this size, and compression is decent (I owned a synthetic bag before and would never go back - you can't beat down for warmth, weight, and compressibility).
The other nifty feature of BA bags is the integrated pad sleeve in lieu of fill in the bottom of the bag. This sleeve is cut for a 20" wide mummy cut; I stuffed my new 20" regular length Thermarest NeoAir Trekker in, and it sticks out the top quite a bit because the bottom opening in the sleeve is tapered for a mummy cut. But enough of it fit to stop just at my ankles - I'm thinking I may do some surgery on the sleeve to allow my rectangular pad to slide through.
If comfort is your primary concern over weight, size, and warmth, this bag is a great choice. Great color too. So far, love it.