I've never gotten an LCD with dead pixels from Dell (I've had a 2001, 2005, and now a 2405 and none of them came with any). My 2001 developed 1 or 2 after a few months (but nothing that bugged me so I didn't mind too much).
I'm not really sure what their dead pixel policy is, or if they even have a set amount. I know that within the first 21 days you can return it for a new replacement if you have any problem with it (dead pixels, backlight, other screen issues, etc.). After that, I think you can still return it for any problem with the screen (including dead pixels) but you'll get a refurbished one as a replacement.