Juanjo,
I recently did a leap of faith myself with powerbook g4 and I couldnt agree more with Nick. I have been a KDE/ Xp user myself but only now do I realize what I was missing. Using OS X provided me a no frills approach interms of usability along with the power of unix. With usability .. it might be a bit confusing but its only for a short period. And with respect to applications we have openoffice version for Mac OSx called Neooffice. I have been discovering that there are a very good number of applications supported on Mac.
check this link:
http://www.kernelthread.com/mac/osx/
