To clarify my statement above, the reasons I consider an 89 invaluable are:
Early on, it lets you fiddle around until you actually understand the rules -- using your
own problems, rather than ones the teacher assigns.
Later on, you can use it to do a lot of the "grunt work" for various problems.
Towards the end, when it is no longer able to do problems for you, you can still use it to store your notes, including various rules and formulas.
When doing any math on it, it frequently has a function, somewhere, to help you out, if only you know what the function is, where it is, and how to use it
Its a lot better than even an 86 at formating whatever you put into it, as well as providing easy access to decimal or exact output for just about any equation you want to put in.
