I can't speak on C# vs Python or C# vs. Lisp, since I haven't coded in either of those languages. I can speak on C# vs. php - I just finished a job with php and started C#. Originally,I thought I loved it because of the library (ie dataset, dataview,gridview), and garbage collection. Then the object orientedness of it all got really, really hard to implement rapidly. I may still use it to write sockets and hwnd stuff for windows (I'm a game dev), but for web stuff, I'll stick with php and maybe learn py.
well at the "planned" level, nothing. At the throwaway level, everything. Things that would take ten seconds in php (like a simple post form to a db) could end up taking 2-3 hours in C#/.NET
