What's the particular benefit to writing .NET for a non-windows environment? (other than say, wasabi or something like that)
The only thing I can think of is language preference. I like C# a lot better than Java, mainly because of familiarity, but I understand that Java has introduced a lot of nice language features lately.
That's pretty fair, but why not just use a windows server, you can get them cheap, and you can even get windows VPS at a pretty reasonable price.
That being said, fogbugz does use mono for any *nix installs (for some things)