Yes you were right , all problems disappeared after a a factory reset, which I have noticed that it kept the latest ROM installed.
Pretty annoying because I had to reinstall more than 100 apps from the market, since The Android sync software allows syncing only contacts and calendar but not apps and setting.
Anyway , now it's just fine.
I'm not sure if it became any faster though.
For sure it did'nt become slower , but my Hero has always been lightening fast since day one, maybe the improvements are visible only on even older ROMs or will manifest themselves only in the future.
We surely have a great phone but I really hope I will not have to go through all this process one more time: I spent 5 or 6 hours to redownload and reinstall all apps and I will need at least 2 or 3 more to rebuild my 3 "scenes" with my wallpapers, rings, apps, shortcuts etc.
I dont understand why I can back up and restore in few minutes all settings of my HTC touchHD and of my N97 but not for the Hero.