The TI 89 Titanium is an awesome calculator. What most people need to know is that this calculator is a bit too advanced for most people. In other words, most people will never use or need the full capabilities of this calculator. I recommend that unless you are 100% sure that you will use this calculator to the fullest, you buy the TI 86. I have both so I know they are both good calculators.
Also, this calculator retails for $149.99 at Best Buy, so don't be dumb and raise the price above that.