I never purposely keyword stuff my pages but sometimes a keyword just naturally comes up a lot. I think I may have got penalized for "keyword stuffing" on a page... But I'm not really sure what it is ... because I also just got a lot of links to it (although I am careful to vary incoming anchor text.) oops... Didn't really mean to bump this thread up either. I actually found this thread in a search on Google for this issue...
i think keyword density is important, google give much importance to Meta Tag as well as key word that you are searching, when ever i make changes i check my site using google webmaster tool for any issue thats google having with my website.