I use a school-issued TI-92+ in my Calculus for Business class. It's like an 89 but with a QWERTY keyboard and a significantly bigger screen. And it uses AA batteries instead of the shitty AAA. If your professor allows it, get a used TI-92+ on Ebay.

I also have a TI-89 Titanium and a TI-86. The 92 is teh winnar.

If the 92 weren't so huge =) At least you can fake carrying around a 89 without looking like you're carrying a small laptop. If you wanted a QWERTY keyboard, get one of those small Sony Viao's and put Maple, Matlab, etc on it. I understand there's a huge price difference between the two, so this isn't a suggestion most people would go for, but for the size, you're better off with a small laptop with some powerful math software on it.

I also believe a small solar power calulator is also essential to have with you too. Something simple (Casio actually made a nice one about 5 or 6 years ago, that served me very well). Sometimes you just need to do a few simple calculations, and its incredibly silly to take out a huge monster. Also, when the batteries run out, a backup is always nice to have.

Also if you are so desperate for a qwerty keyboard, you can buy one for youe ti89 for like $20.

TI-92 or TI-92 plus, tons of features, can do everything the others can do and more, also has lots of memory and when your ahead of the class and bored it even has enough to put a couple games/ebooks in it. awesome calculator, beats the pants off of TI-83,89.

I've had a TI-86 for the past 6 years, since 8th grade and now into my Calc 1 class. As long as when the instructor is talking you can translate from "TI-83" to "TI-86" language, you'll be fine.