FYI: I tried restoring a 925 backup to a 640 and it messed up my start screen (can't even explain what happened, really weird, like half the screen was unusable, should have saved a screenshot). So restoring a backup might not work for you anyway.
Would not surprise me. Well, I can always wipe and start from scratch. My 520 is actually, my second 520, the first one was replaced under warranty because the USB connection stopped working. So, I restored my backup to the new 520. Worked OK. But to a 640, might not. The situation is, of course, complicated by the fact that my current 520 is incapable of creating a current backup, as I say. Maybe I can fix that, maybe not, before I try a restore. Fact is, most all of the apps I use on a regular basis were already on the phone 7 months ago, and the backup that's out there is from back then. My settings? Well, presumably I can reset them, so it wouldn't seem to be a critical matter that I won't have my current settings.
Mainly, I do this stuff:
Listen to music... the app (I think) is X box, somehow. I think it was on there initially
Amazing Weather HD (great app)
One of my battery apps (of which I have ~5) is nice
Kindle Books
MyAppFree
New York Times
Camera (and camera roll), built in stuff, I think
--------
I have other apps, some of them really neat, a bunch that I should use, but don't much... yet, Evernote included, and others...
I really have too many apps (via MyAppFree), many of which are fluff, many probably well worth checking out but I haven't.
I should do more internet searching, Google, etc., but am not in the habit. I should! I do almost all of stuff like that with my PCs.