I didn't use my TI-83+ in college at all. My calculus courses wouldn't let us use any calculators, nor would physics.
True enough, my Physics 1 class allowed only a SCIENTIFIC calculator. On the other hand, my Physics II class wouldn't even allow a calculator, because everything was done symbolically. The last math class I took was (after Calc III) Diff Eq, and none of the work in there really needed a calculator, nor do I think he allowed it. However, at least a TI-83 is useful for some other classes, namely Digital Signal Processing (DSP), because you tend to need to do a lot of algebra involving complex numbers, and that isn't the easiest thing in the world to do by hand. A calculator makes your life in that class a lot easier (a LOT).
... But again, note that you don't need a Ti-89 or above. A Ti-83 does just fine (in fact, I think some scientific ones also did that job just fine...).
As for Physics III, I'll have to see what his tests are like, I'm in it right now.... but they're not likely to need it much, looking at the homeworks.
The point is this: people seriously overestimate just how much they need from a fricken calculator! Seriously! Ti-83 for almost all purposes is just fine... it's the most you should consider getting. You don't need anything above it, even if you're going into engineering. It may make your life easier every once in a while but most of the time you'll have a computer sitting in front of you with a program that you can use for even THOSE things. An 89 just isn't worth it.
