I personally didn't like this product very much. I ended up just writting my code in vim and then creating a new project with exsisting files just to package it up for the installer.
Calling .net objects from perl is easy enough, and this alone is worth the money to get a decent gui on win32 (if you develop commercially). Although most of the other .net libraries already exist for perl. I actually wrote my gui in c# so I could use the gui editor and then called my perl code from c#.
Making calls to perl code from c++, c#, or vb only takes a little modification of your perl code. The problem I ran into was complex data structures. I had lots of trouble passing HoH and AoH data structures between c# and perl. I ended up writing an iterater to navigate the structure.
Activestate NEEDS more documentation. While they do have some, it is not nearly enough and sparse at times. Another problem is finding the dlls required for distribution (the answer is on the perlnet mailing list now).
I also ran across some bugs, but activestate has put the fixes in their current version (it took about two weeks to get a bug fix).
Overall, I think it is a good product. It has issues, but it is also a fairly new product. The ability to use c++, c# and vb with perl is very nice (easier then writing xs) and helps open to door for more people to use perl in their projects.