relax microsoft, you've nothing to worry about
I've been developing on linux for a few months now after using windows for awhile. It's like going back in time to 1990, when I was a UNIX developer.
The O/S is rock-solid, never crashes, never needs rebooting. Might be promising for server-side apps.
However, the user and dev software is another story; feature-light, flakey, complex, undocumented, unhelpful. To use linux you have to be an expert in everything, from system administration to network protocols, to the internals of every tool you use. What a joy it was to return to visual studio for a personal project and be able to concentrate on writing code for a change. It's possible there is a magical set of tools that all run flawlessly and are well documented, but I don't have 'em. Sigh.
The number one reason why OOo isn't ready for business is that it chokes to death on long or complex documents or long editing sessions. It's great for one-page memos. Gimp? Terrific. I use it, even on windows. I just wish I could understand what the other 90% of it does. Evolution? crashes 10 times a day trying to talk with Exchange Server. Firefox? Stable enough for brief browsing sessions, but the error log is a confidence-destroying horror if you start it from the command line. And ugly? Wow. I work with several distros and they're only so-so at figuring out my mainstream hardware. I haven't even tried to get anything like a music player working.
If you're a windows developer wondering if you should make the leap to linux, relax. Microsoft isn't going away any time soon. You are already using the best dev tools available, sad though that is to hear.