Absolutely not!
I know a couple of kids who bought the 2006 FA and halfway thru their studying, realized there was new information in the 2007 FA and had to switch.
At that point, they could either a) transcribe all they've written in the 2006 to the 2007 or b) carry around both copies like dopes.
Conclusion? Now is not the time to play cheapskate. Buy the 2007, make it worth the money by studying well, and you'll never have to worry about whether or not using an older version of FA may or may not have impacted your scores.