i use my pb for pretty much anything - except gaming and making coffee...
one thing which hasn't been mentioned so far is music - connect it to your stereo and you'll never use your cd player again! mmmm - i love itunes...
but off course - pretty much anything which can be done on mac can be done on pc and vice versa!
btw - it seem mac is very popular not only w graphics, design, video and so on, but music/sound editing as well?!