I find it interesting that HTC woud confirm "severe battery drain issues" but a good number of users with 2.2 have seen no change in battery or better.
I myself did see a drop in battery the first couple days, but it did even out, and now my battery is good as ever.
Said it in several other posts, other posters have relayed the same message. Initially after your update you will see a drop in battery life. One reason my be because you are having a grand ol time checking out the new Froyo features thus leading to more phone use. Another reason could be because the battery calibration was reset with the update and when its recalibrate days down the line battery life seems improved.
My suggestion is give it a couple days and see if the battery is better or not. Don't worry too much about checking in on apps to see if they are running, or trying to kill apps because then you end up wasting time and battery using your app killers. If after a couple days it still seems shotty then we can turn to software or hardware defects....or even just individual users and apps.
oh yeah, and a factory reset really does make a difference. Many reports of this.
I say this just out of my own personal experience with Froyo.