It really depends on what you're most comfortable using. I've written code using Microsoft's C++, Visual Basic, VBScript, and C#. The easiest is probably C# because of how easily it integrates with COM (and because I'm more used to C++ than VB). You should be able to write code using any language/development package that supports COM. So Python, Delphi, JavaScript, etc. are all possiblities.
The only other thing to be aware of is that the help file samples are all written in C++ and VB. Not a big deal to translate them to other languages if your used to it.
John Bartak