5.1 doesn't fix the mobile radio drain bug so in my book while 5.1 fixes a lot of issues, its still a meh overall experience.
I finally had to upgrade my OPO to Lolliflop. The Google Play Services battery drain fix I was using in 4.4.4 suddenly stopped working (Google Play Services started crashing every 10 seconds) and I didn't want to mess around with finding another fix.
So I installed the latest official 5.1.1 release. I managed to get decent batery life by rooting, installing Xposed, the Deep Sleep battery fix and the Mobile Radio bug fix. The only drawback now is that I only get notifications once an hour, but at least battery life is similar to 4.4.4 with the Play Services fix.
It's ridiculous that you have to hack the OS to fix these kinds of bugs (both in KitKat and Lollipop). I really hope Android M has fixed these ridiculous battery drain bugs, otherwise I'm moving to another mobile OS for my next phone. It seems Google doesn't take battery life and memory leak issues seriously at all.