Sadly, yes, unless your site is aimed solely at technologically savvy users. Or even technologically awake users.

Sad as it is, most sources indicate that IE still has 70-75% of the browser market share overall, and ~40% of IE users are still on IE6. So roughly 30% of the web browsing market is on IE6, which is a rather large subset to simply ignore.

Like it or not (and none of us do), the bulk of sites out there are stuck with supporting IE6 for the near future.