There are some rather nice simultaneous 2.4/5GHz band routers out now. The Linksys E3000 and E4200
come to mind. That said, I've used the DGL 4500 as well and it was a pleasure to work with it and was quite stable. Port forwarding, IP address reservations, and DMZ were all straight forward and easy to set up. It also is one of the few consumer routers I've worked with that doesn't shit a brick when I do massive intranet transfers between machines and devices (massive as in several terabytes in a single constant transfer). It also was able to handle the home network at the time which consisted of around a dozen wireless, mostly N with some G, devices and around the same number of wired devices as well. Netgear and Belkin have never been able to cope with that level of load in my experience even after I tried their N1 Vision router
. At my apartment I currently use the Linksys E2000 which works well enough for the handful of devices which are on it though I wouldn't recommend it for anyone prone to large network transfers or higher quantities of devices.
I really did like the DGL 4500 but couldn't justify the massive cost difference for a tiny apartment with such a small number of devices. The idea of a simultaneous dual-band router is extremely appealing though. As it stands not all of my devices are compatible with the 5GHz band which means that, with my current E2000 or even if I had the DGL 4500, I'd be stuck either not having access on those devices or sticking with the oversaturated 2.4GHz band (my apartment building has some 60 or so wireless networks running, with the vast majority being on the 2.4GHz band either 802.11g/n). I figure my next router, when I move out of here, will definitely be a simultaneous dual-band beast as I'll be looking at doing heavy transfers to a local server at that point.