I noticed the same thing right after I received my GB update. Over time it seems to have gotten better, and here's my observation. I noticed right after the update that the CPU was operating at a much higher level than it was before, and it seemed to be multiple apps that were consuming an inordinate amount of CPU compared to before the update.
I wasn't sure what to do, but then started to notice a strange phenomena. Apps that updated after the GB update seemed to run smoother, and definitely consumed far less CPU. I continued to monitor CPU through task manager and found several apps that even after their latest updates seemed to not handle operating under GB very well. I either deleted those apps, or found alternatives that worked better.
The net result is that my battery life is now back to pre-update levels. I do still experience some sluggish operation, which is quite frustrating, but it doesn't sound as bad as what you are experiencing.
I'm not a phone guru, but do tend to notice when things change, and have an insatiable curiosity to figure out why. That's my experience. Hope you find it helpful!
BTW, I used to have an app that showed me graphically my battery level. I loved having that feature, but that was one of my worst offending apps after the GB update. I tried others to no avail. When I completely removed any apps that monitored battery level, my performance improved almost back to pre-GB levels.
Anyway, like I said, I'm not a phone guru, but I do tend to notice correlations even if I never figure out the causality.
Cheers!