We have (prefinished) hardwoods downstairs (that we replaced the old, yucky-tannish but supposed to be light blue carpeting with) and still have carpeting upstairs, that I would love to get rid of (it's 15 years old and while still looks nice, it is harboring something that stirs up my allergies).
I've also heard that steam cleaning can make either some mold/musty issues or dust mite issues (I can't remember which, I was hoping that someone in this thread would mention it, lol) in carpeting worse, which has really put me in a catch 22, because it needs cleaned, and it needs deep cleaned. I really want to just replace it, but if we do, it will need to be carpeting again, because (as my dh says) it will sound like a bowling alley up there otherwise, lol. I'd like to get Berber, but with 4 cats and a dog (the "bowlers"), that's kinda out too. Blah.
I do believe that my indoor allergies have improved with having hardwoods and vinyl downstairs in the main living area, though, if that helps any. I do have area rugs (carpeting for the feet without the underpad that can't be cleaned <img src="i/expressions/face-icon-small-wink.gif" border="0"> ). I would think (JMHO, of course), that if allergies are not a problem for your family, I wouldn't sweat the carpet issue just yet.