In dilemma regarding 512 devices.

Using it on my L630 this latest build .107 is slow as hell, I seriously dunno what MS has changed for it to become so slow and unstable.

Previous builds were way faster.
 
Email Threads, Messaging enhancements, pretty much the Denim stuff the 520/521s never got + the background features for the start screen. That was enough to make me upgrade it haha
 
ok, so I installed the latest .122 and i must say, wow, still got some more tests to run, but it's way smoother than the .107.

And yes, it is worth the sacrifice.