We got something similar in the Dutch Army under the SMP (Soldier Modernisation Package - we're becoming more and more Anglophone over here...).
It's nice to sleep in, really comfy; but when you have a crash move it is a serious problem to get out of it quickly. And working three zippers with cold, wet fingers can be difficult to say the least. Also, when not properly assembled I've seen (and heard ) people getting tied up in their bivvy bag-inner bag - outer bag combo.
I've used one; its a very clever design as all three layers - inner thin, outer warm and goretex - snap together along mthe right hand side and so you can "burst out" if needed. the hood also velcros into place so no worrying about which way is up, or having dreams about being suffocated.
Downside: its not for the tall; I'm 1.80m and found it snug, almost too short. Bit big, too, but the inner plus gortex outer can be useful.