All good advice and recommendations here, Mr. Hoffman.
A few of bad parts and mechanical issues that their failure caused were, as pointed out earlier, substantially worked out by Triumph as they got the beast into the latter half of their '07 production run. I made sure that the "upgrade kit" (a pkg of parts and labor Triumph bundled and generally offered gratis to address fixing the known problems) had been performed on my ride before I purchased her.
Not sure that anyone has mentioned this so far, but the Rocket III takes a bit longer than other big bikes for the valves to seat properly. Therefore, a valve inspection and/or adjustment is called for at approx. 10K miles. Thereafter the valves need only be checked at 20K mile intervals. if the 08'T you're looking at is at approaching, at or beyond the 10K mi mark, you'll want to insure the the valve work has been done. If it has not, I'd suggest you make that a bargaining chip for a slightly better sale price as the work will run you as little as about $200-250 if all of the valves are in tolerance or from $400-$1000+ depending on how many valves are out. Of course, much of this expense will be determined by the quality and honesty of your local dealers, so do some homework on the Triumph dealership network in your area.
I have had an 07' Std, nicely dressed, for just one season, now. For most of the 9,500 mi I put on her she was problem free and an absolute joy. My primary Throttle Position Sensor (a known problem on many earlier R3s) failed late in the year, but Triumph stepped up and payed for the $110 part and I payed for the labor... quite fair since I'm the second owner and the bike was about 18 mos. out of warranty.
There are no viable reasons not to go ahead with your purchase, IMO! You will undoubtedly not regret becoming a Rocket III Captain. We all look forward to congratulating you when do pull the trigger. Resistance is futile!
Enjoy the ride and let us know if you need any further assistance!