I've done it much easier..
Download
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Which is the flash tool Download FlashTool version 0.2.9.1 Beta :
Then all you have to do is to put your phone into USB debugger mode, conntect phone, then run the flasher...
Then
Root - Phone will restart after it's done, (I think it'll install busy box too)
Then install X recovery....
Then when phone is restarting (with SE logo) keep pressing back button untill you get to xrecovery mode,
Then back up your rom

Then run the flasher again with phone connected...
then use the Flash button to flash your phone to the rom you want..
or you can use optimize to install JIT, which is really cool

, or APK installer to install some stuff to your phone..
then Clean button will allow you to delete the junk apps and it'll save a copy of it in the app_copy folder....
Please correct me if i'm wrong.. I only did it last night, and I haven't flashed my phone to other roms yet, i've just fiddled around with the flasher to speed my existing rom...