Qt version question

What's the general default version of Qt on Linux?

I have 3.3 on my latest FC6.

Since Mac/Win32 versions of Qt are currently at 4.x, it looks like I'll need to support 4.x rather than 3.x.

Anyone have any issues with that?

Well, I've decided that it *has* to be Qt4.x+, because it makes for an easier life for me...

Yes, sorry, I got so angry when my flakey ubuntu refused to download kate + friends due to ip64 compatibility issues with my rooted modem I didn't get to see what qt would get installed with it.