I have the exact Dell monitor you're thinking about. The ACD's have a 16ms response time, compared to the Dell's 5ms. While the ACD may display color more accurately for designers, the Dell is perfect for all around use. I use it to game, watch movies, work on documents, edit photos and movies, and just surf the internet. It came with no dead pixels and shipped promptly. The Dell is a fantastic deal. For an inch less, you'd be paying twice as much for the ACD. It just doesn't seem worth it to me.
Hope this helps. Good luck with your purchase.