The GLT and the T5 are essentially the exact same car, only the T5 is...well...better. The engine internals (conn. rods, valves) are better, as is the suspension. No more maintenance, although switching to synthetic oil if it's not using it already could only do good things for it. Without maintenance records, I'd check the Carfax and make sure it hasn't been in any accidents; other than that, just give the car a good once-over and make sure everything works!

That said, they're probably not as reliable as the old-school Volvos that NEVER break..."advanced" technology complicates ALL things, and there are common problems associated with them all, but going on almost 2 1/2 years, mine has been great to me - nothing has really outright broken on mine, and usually the things that go wrong are nothing too hard for you to fix yourself. With an 11-year-old car though, things are old and some minor repairs will no doubt come up.