I'm a HTC Hero user (US, CDMA version) on Sprint, and I'm currently running a Cyanogen build on it. I've actually run a number of different ROMs on my phone, Cyanogen just tends to be the most stable, and cruft-free. There are step by step guides for rooting and installing a new bootloader to your phone, which are all fairly easy to follow. Once you've done that, it's just a matter of dropping the ROM image onto your SD card, booting into recovery mode, and hitting install. Not a one click solution, but given an hour or two, simple to follow.
As to the quality of the ROMs themselves, it (of course) varies. I've never had anything that was just outright unusable (except maybe the stock ROM -- it was ungodly slow). The first few ROMs I used crashed about once or twice a week, which was annoying, but typically happened while I wasn't using the phone, so I just felt it vibrate in my pocket. Now that I've switched to Cyanogen though, this problem has completely disappeared, and the phone is very quick, especially compared to the stock image. Seriously, if anyone else has a HTC Hero, I'd recommend rooting and moving to the Cyanogen mod ROM, it's like having a completely different phone. Plus, I get to be on 2.2, while the stock ROM is still on 2.1
The only downside of it so far is that I couldn't manage to get my carrier voicemail working with the image. There may be a workaround for this, I just haven't looked. Since Google Voice integrates so well with the handset, you can tell your phone to forward all of your voice mail to VG, but not use it for any thing else (or choose when to use it for calls, etc., it's amazingly flexible).
I use the xda-developers forum for all of my rooting and ROM needs, and you can probably browse some of the feedback and FAQs there if you have any questions. Alternatively, my e-mail is in my profile if you have any questions you can't seem to find answers to.