<p>Yes, definitely get a TI-89 if you can afford it. I was an engineering undergrad and am now a grad student in engineering. I attribute at least a full extra point of my GPA to my TI-89 abilities. </p>
<p>Many classes involving math that aren’t in the MATH department don’t care what calculator you use, examples include engineering classes, econ classes, stats and probability classes, etc. The TI-89 can do symbolic solving, for example if you type into its solver sin(x)/cos(x) it will return an answer of tan(x). Even for classes that don’t allow you to use a calculator on exams, the 89 is still invaluable for homework. Furthermore, the TI-89’s screen supports more lines of text then the lower model TI’s and it has a large amount of extra memory. This lets you put cheat notes on it for use during exams using its built in text editor.</p>
<p>With regard to calc, if depends on your major and how much calc you’ll be using later in college/life. I took AP credit for my intro calc classes but still had to take 3 more semesters of more advanced courses. In retrospect my GPA would have been happier if I aced those first semester courses.</p>