SB600 or 900?

Hi

Looking to buy my first flash gun and like the look of the SB 600 and the all signing all dancing SB 900.

Is it worth the extra £90 to push to the 900 do you think? I've not used any external flash before but don't want to buy something that limits me for the sake of a bit extra cash. I think I'm almost answering my own question here but any users of either here that can share your experience/advise?

gratefully received!

thanks