I have used pretty much every TI graphing calculator and my all time favorite is the TI-89. Not the new TI-89 Titanium though, the buttons sucks.
All other calculators have crappy screens and problem displays. Further, the solving capability is way lacking. MBrown, if you can use a computer, you can use a TI-89. It does take a wee bit of time to get used to the interface and the functions, but in the end, the TI-89 is invaluable.