The '09 is the best model to have if you crave for the '05-'09 body style as Ford had ironed out most of the bugs that came in earlier models, including the spark plugs ('09 have one-piece plugs that don't break like the earlier two-piece version).
That's good to know about the plugs. Just curious, what is the gear ratio on 09? I got lucky on my 06, it has 3:55 from the factory but I didn't know that till after I bought it. There's a white tag on the rear end that showed the ratio, is it the same with the 09?
Check the hood very carefully, especially the front edge and the underside, for paint bubbling. If you find it, don't think you're going to grab a nice clean hood from a boneyard or CL for cheap...most of them are either pre-bubbled, outrageously priced, or both.
If there's any kind of blackout panel (especially the magnetic kind) on the decklid, look for rust behind it.