Mine is an '07. They went to the 4.7 in '09. The 4.7 was noted as having more torque but being a little less satisfying at the top end and some people say the 4.3 sounds better.
There really is very little that goes wrong with these cars. They're very solid. Some cars have a timing cover seal leak that Aston has since addressed. Leather on some dashboard parts can shrink and need replacement and the door on the GPS system is fragile. Like any exotic, they are expensive to get work on. These cars have a transaxle and a torque tube, so there's alot to remove to replace a clutch, it's about $7,000 from the dealer. In general it has cost me about $300 or so a year in maintenance.
If you're looking to buy one, THE definitive book to buy is this one:
Aston Martin Review