Sorry for the caps but I just stumbled upon this method and it has worked flawlessly over the past few Roms I have used it on. From Jrummy, back to BB, and whoever else's Rom you'd like to use.
1. BACKUP your entire rom through rom manager
2. Reboot into recovery.
3. wipe (as you normally should 3X ).
4.install new rom.
5. Goto main screen of rom manager, click Nandroid>Advanced restore>select your ROM Backup you just created> Restore data.
New freshly installed rom, and ALL of your data just the way it was. Nothing missing and all the information from the new rom you just flashed should not be affected, since we only restored the DATA part.
Works GREAT and makes trying newer / different roms STUPID EASY!
SO simple yet so great.
Also THANK YOU PETE for all of your hard work. It is very much appreciated.