I was in your shoes about a month ago. Yes, this topic has been beaten to death, but every thread helped me when making my decision.
I knew I wanted a Triumph, but it came down to the Thruxton and the Bonneville SE/Black. It's a common dilemma, but I knew I'd immediately want to sport up the Bonnie with chopped fenders, different bars, seat cowl, etc. However, I am your age and I wasn't sure for how many years I'd be able to enjoy the clip-on handlebars. That was truly the only thing keeping me from the Thruxton so I dug a little deeper.
I bought my 07 Thruxton, black with white stripes, just shy of a month ago. The weather here on the East coast hasn't been great, so I've only managed to put 140 easy going miles on her. The riding position is a bit agressive - I should mention my last bike was a Honda 919 so the bar position was closer to standard on that - but it feels good overall. I like the rearset positions, but I have already been kicking around the idea of "improving" the bar setup, an idea at which many of the hardcore members will scoff. No matter what I wind up doing it's all about what's comfortable enough for me so that I won't think twice about jumping on the bike as often as possible.
I sometimes wonder if I should have gone with the Bonnie, but then I go in the garage the next morning and smile like an idiot. Don't get me wrong, the B.Black is sick (esp. check out Sweatmachine's bike) but once again it's all about me and what
I wanted.
Definitely take a riding course. It's basically free here in PA for residents, but I would gladly pay for it if my state didn't cover it. Your insurance alone should make it worthwhile after a short while, but it shouldn't be a monetary decision at all. Even though you've toyed around on two wheels before it will take your confidence to new levels.
Bottom line - the Thruxton is incredible. It's not going to outrun Japanese sportbikes, but most of us who purchased these bikes aren't looking to thrash them from redlight to redlight. Once you get your license take advatage of the Triumph test ride program that most dealers participate in. (That's a great feature you won't find at most other shops.) Also, find your local RAT group and get together with those guys.
The Triumph bug bit me a few months ago so be sure to warn your significant other. If you don't have one of those yet this bike might help with that, too!
Good luck, keep us posted.