The TI-84 Plus is a great graphing calculator. Compared to the TI 83, the 84 Plus is an all-around improvement and well worth the extra $15-$20. Another plus is that the calc is also extremely easy to hook up to your computer to transfer Apps and updates using the included USB cable.
Just one con: The rubber on the cover and on the back that are supposed to be for giving the calc grip when resting on a table fall out very easily
I have used this calc for over four years and besides that one aesthetic glich, have not found only problems with it.
Texas Instruments - TI 84 Plus is recommended by iamthinking