If you use a really old version of Open Office it is not another Sun Microsystems abomination. Otherwise, LibreOffice is the best by a vast stretch.
OpenOffice is now an Apache project, actually. The code was donated and has been combed of stuff that made it incompatible with the Apache licence. At least both OO and LibreO use ODF rather than that abominable OOXML "standard". Most of the objectionable (for me) stuff in Win7 appeared in vista first. I just switch to the NT4-style taskbar. The ability to type a program name into the menu search is about the only thing I'd call an enhancement.
Well, it depends on how much memory your computer has. The last one I used was really bad in that regard so XP worked faster, but the one I'm using right now is better with Win7.
