When it comes down to it, it doesn't matter if there are a billion users of Iron Python, you can't have 1 developer in a team just suddenly decide they are going to write in a language that no one else on the team knows anything about. If it's a C# team, you can't have 1 developer who suddenly decides to write some bits in C++, even though C++ is a hugely popular language. If your the team leader/senior programmer, just tell him it's not an option. Tell him it can be looked into it for the future, but either everyone on the team learns it, or no one uses it. Language/framework choices are management/lead decisions, not ones to be made at a whim by the programmers. If your not in a position to do that, raise the issue with your manager, highlight your concerns, and make sure they are aware of the potential issues. (As others have said. Python is popular and in heavy use, but IronPython use is pretty much non-existent.)
Simon
