Why not Opera?
The new version 4.0beta5 is enough stable and works well on linux. It's light and fast and I use it for my daily browsing now. The 30 days limits (true days of use, not calendar days) resets on each new beta release and till now i didn't reached this limit.
I prefer it also in the Windows environment, where the new release 5 of Opera is free.
OK, it's not open source, it is still proprietary and the free version displays an advertising banner (but it's not annoying), may be not 100% as rich as the bigger browsers(but i found less problems with Opera than with Netscape 4.7), but if you talk about MS IE and a "war of browsers" remember that also IE is not open, neither free (don't you pay to have Windows, to make it works?).