My DGL-4500 has been up for a few weeks since Ru-fi-oh put out the phase 3 beta i have a WAN and a LAN configured  this is how it looks to be simple
                                       |Xbox 360                |Xbox 360
COX---Modem---DGL-4500--|Switch--------------|Desktop
                                       |Desktop                  |Desktop                |PS3
                                       |6 Wireless Devices    |Belkin Router-------|Desktop
so yes i have alot of stuff connected to it i havent had any problems with it the 6 wireless devices are (Wii, 2 Laptops, 2 Desktops, and an Ipod Touch. 
yes that is a rough sketch but we as a family do alot of stuff on it. (IM's, Downloads, Uploads, Gaming, shopping, Schooling, and Video calling, All at once i usually nvr have lag issue but im only getting the 20Mbs from Cox like im suppose to be getting. so i dont know how others r having problems but mine is busy 24/7