The guest account works as advertised, although the features are rather limited. There's no traffic management so guest account can monopolize the available bandwidth. There's also no cron based utility to turn off the guest account after hourse. Still, it's useful.
The Belkin N1 Vision F5D8232-4 wireless router
also has a guest account. See Page 58 of the user manual. It works a bit differently. The MyEssentials router uses the same SSID for both the normal and guest accounts, using different WPA phrases to distinguish between accounts. The N1 Vision users different SSID's each of which also have seperate encryption keys. The encryption type has to be the same as the normal SSID, so you can't run WPA on the normal SSID, and no encryption on the guest account.
With DD-WRT and other alternative firmware, it's possible to run a guest account by setting up seperate VLAN's for each account. However, it's far from simple or elegant:
I haven't tried it.
Probably the most sensible method would be to run one of the assorted "captive portal" apps on the router. Some of these offer multiple levels of access.
DD-WRT includes built in support for Sputnik, WiFiDog and Chilispot under: Services -> Hotspot
plus a firmware version for running a FON type hotspot: