hehe, I guess nobody knows...
I have Mathcad 2000i which produces pretty good graphs but the program is unstable - it crashes whenever I type in anything with a division sign (

) and also messes up on graphs with complex roots. Aside from the technical issues, the main beef I have with it is that the interface for typing in equations is absolutely horrible; I can never type anything in right without making several mistakes, and trying to correct the errors messes it up even more.

Otherwise, the graphs look fine:

It cannot do implicit plots though; the only program that I can find that is capable of 3D implicit graphing is something called NuCalc, but I am not willing to pay $60 on something that I have never heard of and has a completely useless demo.
