I agree with the ones who wouldn't change their 600 for the 300, and i add something really important...
in the PRS-600 you can play tic-tac-toe and other similar games... lol
nah, i'm just kidding, but the touch screen and being able to write or draw is the best part for me... i also like the dicctionary, but i'm sure somebody will install it in the PRS-300 eventually, so its not a big PRO... =]
long story short, i would go definitelly for the PRS-600 time after time...