I was wondering how the tone from a thinline type telecaster varies from that of a standard telecaster. Is the thinline more of just a weight reduction feature or do you get a tone benefit from it as well?
Hmm. If (and it's a big if) there is any tonal effect at all, I would expect it to be a penalty to my ear, not a benefit. - Based on my very limited experience with a Gibson-style semi-hollow. But "good" and "bad" are very subjective when it comes to guitar tone.
Minimal. The Thinline isn't a "real" semihollow - it is routed out purely for weight reduction (back in the late '60s they were low on light cuts of ash at a decent price, and CBS Fender didn't feel like shelling out for more expensive wood) and the f-hole is aesthetic; meanwhile there are no resonating surfaces and the hardware is much the same as a traditional Tele. Like any weight-relieved guitar, the difference is that it's lighter and whatever tonal difference you perceive as a consequence of that (plugged-in, at least, I would say practically none). Also it looks great. There's no reason to discount that bit.
i always feel i get a slightly less tight bass, so if you play a lot of stuff where you want a very tight bass (say heavier stuff), that's worth bearing in mind. other than that, minimal differences as K33nbl4d3 said.
As long as it still has standard tele pickups the audible difference is only very slight if there is any audible difference at all. I agree with Dave MC and think the bass isn't quite as tight but it is very slight and I can only hear it when comparing guitars that use lighter tonewoods. If I play a thinline made with northern ash (which is quite heavy) and then play a solid body tele made from the same ash I can't hear a difference. If I play a thinline made with swamp ash (which is much lighter) and compare it to a solid body tele made with swamp ash the bass from the thinline doesn't sound as tight.
^ I just notice because after about 5 seconds of more tasteful playing I get sick of it and crank the gain up, and I always feel the bass isn't quite so tight (or maybe just the entire frequency response isn't as focussed), which is very noticeable at higher gain settings when you're used to solidbodies.