Good, just misses being great
I'm 6ft 1 and getting in/out isn't easy - the zip could have been another few inches longer it would have got 5 stars. The other minor thing, it's a hot bivy and there's limited ventilation even with the flap open - this is ok in cold and cold wet weather but like a sauna in warm/hot wet weather. I took it to a gear alteration place and they added a head vent on the opposite side to the entry and foot vent to make it comfortably useable year round.
Overall very this is a very durable, robust, extremely waterproof bivy, it's breathable enough to minimize condensation in cold weather and it packs down fairly small. BUT, be prepared to live with the limited entry, and to customize the bag it if you plan to use it in warmer weather (25C/77F or more). Extending the main zip is a technical and expensive modification - I got 2 quotes, both over $250 to extend the main zips!
So far I've used it in the Ruby Mountains in Nevada where I had snow, rain and a bit of everything except warm weather and in Victoria Australia for a few nights where it ranged between 0oC to 30oC (32-86F). Like any tent it's most comfortable in the cooler stuff.
For comfortable use in hotter climates increases natural convection and cross flow with some closeable vents.
I use the bivy with a piece of tyvek cut for a ground sheet (cut large enough to step out on to it and tuck boots, etc under when wet), a regular size neo air and a marmot aspen ultralight bag with silk liner, and it's comfortable down to -10C (14F) even with the ultralight bag. A regular neo air fits nicely and leaves me room for a 35 liter pack in the head end. A large neo air does not fit. It's at the heavier end of bivy's, but at the extreme light end of tents - prefect for solo mountain biking with a lightweight 30-40 litre pack. It includes a tube of seam grip and syringe to apply it - use it on all seams and this bivy is 100% water tight.
I wanted this as a my one go to bivy for all conditions, a tough spec but the black diamond tripod came the closest. With the vent mods it gets 4 stars and only misses out on the 5th as I find the main entry zip is too short.