I used the 2002 edition to study, and I wish I had waited to get the 2003. There do seem to be quite a few changes between the editions. I often had to write things into my book that were printed in my friend's 2003 edition. Also, I thought I would use First Aid to study for class, but it turned out that I didn't, because it is very "bare bones." I would suggest buying the BRS Path and Physio books early & using them for courses. Everything I added into my First Aid was covered in the BRS books, and they are written very succinctly which will help you pick out the most important points from your classes. You'll have plenty of time to get through First Aid after it comes out (in Dec or Jan at the latest).
Just my $.02...