I've tried both of them. I switched from UD 2.5 to PE 4.2 but in all honesty, I don't see too much different between the two of them. However, UD crapped out on me a few times even after doing a fresh install every time. PE 4.2 runs SUPER fast though... the stock font in PE has got to go.. it's ugly
PE4.2 10char
Just like any other ROM it can be. BTW CM6 is Froyo & worth flashing.