I have most of the same extensions installed on both windows and linux, but plugins are a different matter. Windows apps tend to install plugins (wmv, acrobat, .NET, etc.) that I don't use. I've disabled most of them, but not all. In contrast, the only plugin I have in firefox/linux is flash.
Another thing I've noticed is that the js engine in firefox/windows appears to get wedged sometimes. The main symptom is that gmail loads in basic html mode. Restarting the browser fixes that.
There are some mysterious things that happen in firefox/linux, but they aren't as bad. After a long time (many days to weeks), I start to encounter frequent (~.02Hz) brief (sub-1s) freezes (most noticeable when typing into an input box like this). Restarting firefox/linux solves those.
I also have issues with it automatically capitalising login data in forms when I don't want it to (jem -> Jem), but I think this is related to the first issue.
My decision to move was largely based on FireBug and ColorZilla supporting 3.5. The fact that they both do made this a no-brainer for me. The increase in speed and stability is well worth it.
If you still can't make up your mind, why don't you install both versions on the same computer?
I might do that. Thanks.
Otherwise, totally worth it.