.NET is a pretty good framework. Better than any framework linux has to offer.
Or is this that definition of "Linux" that people love these days, which is "whatever free software operating system distribution I happen to be most annoyed with this week"?
I was doing Win32 development for 5 years and concluded the .NET development is the best way to go (Only if you can convince the marketing guy to include the 20MB runtime installer in the package)
In any event, you'll find Gemstone's kit more than accounts for .NET (and Java, for that matter) in the trade/financial space.