If you search around there are plenty of good tutorials out there. Now that 2.1 has been released the custom roms have all become much more stable. I'm currently running Ultimate Droid v10.
I've got a rooted droid running Pete's BB 2.1 v0.8. Works like a charm, but I need to set up Wifi tethering before my iPad gets here. I guess there are a lot of droid users here because this site is owned by the same people who own droidforums.net. An ad banner over there led me to here.
Totally sucks for browsing but it does work as a link to the Internet on the rare occasion I can't find a WiFi connection when traveling.
For replying to email though I do think the tactile feedback from the keyboard is much better than when trying to do email on my iPod touch G2 so I'm not sure I would be so happy with email on the iPhone....but I probably won't know until I try it and then I'll have a 2 year commitment