It probably takes me at least twice as long to perform a task in C++, compared to C#. The syntax of C++ is rather messy, which makes it easier to create errors that are difficult to find. Not only is it faster/easier to write C#, I spend less time in the debugger. And it's always possible to write some code in C++ and throw a managed wrapper around it, should you find something that can't be done (or doesn't perform well enough) in C#.
And of course, Boo makes C# look twisted... The languages keep a'changin, and they usually get better.
But I'm sure there will still be lots of interest in that L# Lisp.NET thing... Lisp's longevity is really rather impressive. Isn't Lisp generally considered to be, like, the third computer language ever invented, or something like that?