I disabled things by hand rather than let it decide for me as it seems a bit too aggressive as you mentioned.
22 hours now since a full charge and a clean install of 5.1.1:
It definitely uses less RAM, about 0.5GB for my general usage. When I'm on a night shift I class myself as a power user and usually find myself needing a battery change/recharge by 11pm. 22 hours from taking it off charge and here is what it looks like:
This was with 4hours screen on time, I think I could have easily got over 5 hours SOT before requiring a charge. However... System and Google play services are never top of the list for me in the past, on 5.0.1 or 4.4.4 last week.
Does this second picture look ok to you? It reads like Google play services kept the phone awake for over an hour and I don't think it should be. Location services are on Power saving mode as always.
In general I like 5.1.1 a lot, it's snappier, a couple of nice fluid animations have crept in and the multi tasking page has massively improved from the lagging mess it was before. So far, thumbs up from me, it's at least on par with 4.4.4 for me in terms of battery time and IMO it looks a bit nicer.