When I got mine new (bought it 3 months after it came on the market), the battery drained quickly. However after a few days, there were some updates and that fixed the battery drain. Regarding the problem I had with upgrading to the newer andriod: no the performance manager did not fix the issue. I had to boot my phone while holding some button combination if I remember correctly. That would flush all the remaining files of the update that were no longer needed.