I got it when it just started shipping, and I think it was generally worth the $150 for the upgrade. it's not as big a difference as between 5 and 6 (assuming one had no experience with 5.5 like me), but its got some cool new features, and OS X support allowed me to finally move almost everything over to OS X (still have to go back to OS9 and PS 6 though to print....damn crappy Epson OS X drivers).
the only thing that really pisses me off is that the old filters don't work >_<
I'm surprised somebody hasnt tried to write something that works around this