I completely switched to Linux some months ago and I'm quite happy with it.
Unfortunately there is still a lot of Windows only software. For the most stuff there is a free and open equivalent but when it comes to mobile (J2ME) SDKs / emulators the only way to go is usually the old(!) WTK (2.5.2).
I just wanted to share the information that some really nice guy at the Forum Nokia Discussion Board told us how to run the S40 SDK on Wine.
See: http://discussion.forum.nokia.com/forum/showthread.php?t=90868 (Scroll down to