The telephony part of the HTC Hero works well and I have yet to experience cut-outs or disconnections. I have had a strange echo on a couple of calls but only when on the bus.
The Hero can take quite a while to boot from off, but when booted performance is good. The software seems to be stable and robust. HTC released a firmware and HTC Sense update that improved performance and response time considerably and since then I've never felt the screens should just hurry up and scroll.
The best thing about having an Android based phone is its ability to run multiple tasks at the same time. You can run an app, back out, run another app, then when you come back to the previous app it usually starts immediately as it was already running in the background.
Be aware though that you should spend some time housekeeping your tasks, and killing off the ones that are still hanging around that you are not using but which are using up valuable phone resources. Download a Task Killer app from the Android Market and watch those resources get reclaimed.
The tech specs for the HTC Hero give between 420 and 470 minutes of talk time and between 440 and 750 hours of standby time (depending on network and usage). I've found, even with Wi-Fi switched on almost continuously that I get up to a week of phone use when I am using email, text and the odd phone call before I have to recharge. That is cut drastically if I start using the phone to listen to music.