It depends on whether you need to make it work for as many people as possible. I can only speak for the website I've got Google Analytics on, but about 20% of the visits are IE6, another 15% are IE7. If you can afford to drop a potential 35% of your audience, go for it.
(Here's a wikipedia article on browser share, with a breakdown of IE usage. The official stats are strikingly similar to those I cited above.)
