If you see the panel specifications of Dell, the Grey to Grey response time is 8ms. The black to white response will be far higher for all the panels. While Dell/Apple quotes the average case response time, Viewsonic, samsung and others quote the best response time (which is the g2g). So The Dell response times are as good as Viewsonic 2025wm etc. The 2407 has a g2g of 6ms.
I was a bit skeptical at first about the performance of an LCD for games and after seeing my new Dell 2007WFP in action all my doubts were removed.