Also, price will be going up as of v1.0. There was also mention of additional content available only to pre release orders so you'll get content you'd otherwise have to pay extra for. Buying it now is a good deal anyway you slice it!
Remember though, any dlc will be £3.25 within a few weeks
Will certainly make me think twice about getting the dlc early.
Stuart, AC has been in a few Steam Sales with the last one as cheap as £20 (other sales have been £23 or so). You could risk waiting to see if it goes on sale again.