Today I ditched my good old reliable custom ROM on my phone, MIUI, and upgraded to the latest dev release of ice cream sandwich by MildWild for my HTC Desire.
The link can be found here.
http://forum.xda-developers.com/showthread.php?t=1453287
The installation was pretty smooth and to play it save I backed up all my information to my main micro SD card and used my spare old card to do the installation.
I'd recommend this for anyone doing a ROM flash. If you don't have a spare, micro SD's are cheap these days so go pick one up.
$8 CAD for an 8GB card at
http://www.canadacomputers.com/
Well worth it.
I had my phone already rooted and had previously had hboot installed. If you don't have them done, you'll need to do both before installing your custom ROM.
I'd suggest checking out the All things Desire root guide over at android forums for info on how to do this.
http://androidforums.com/desire-all-things-root/503471-desire-all-things-root-guide.html
It's actually a pretty simple upgrade.
Root your phone.
Download the ROM.
Put the spare SD card in your phone.
Format the SD card while in the phone.
Mount the phone for USB storage.
Drag the new zipped ROM over to your phone.
Reboot the phone with Power+Vol-Down
Choose install from zip from SD
Choose the zipped ROM and go.
Wait for it to install, reboot and you are done.
All in all it took about 10 minutes to do and now it'll be hours of playing with the phone to see what's new and to tweak it and customize it.
If you've got a phone that is out of warranty I'd highly recommend trying it, but as with everything that is not a factory install. Use at your own risk.
That being said, I've flashed about a dozen custom ROM's onto my phone to try them out and have never once had a problem.
-Colin.