When trying new Roms you will need to do a system wipe and you will lose everything. Some people use Titanium backup to save there apps everything. I personally do not as it sounds like it causes a lot of issues. You might be able to save texts which should not cause conflicts....Maybe someone else who uses it can chime in on that.
When flashing an updated Rom from the same developer, a lot of time they will tell you that you can flash over what you are running. Again, this only applies if it is an updated Rom of the same developer that you are currently running and they will tell you if you need to wipe. Different developer = always wipe clean!!!!!!
Also, a lot of the the custom Roms will come with custom kernels when you flash it and will be tweaked for better battery from the start.
Are you stuck trying to boot from a nandroid backup???
