I also have the 3-play router. I can say that everything is a go for me. Do not rely on the vista network map for this router it is highly inaccurate because, it does not know what what the hell the router is doing, nor does it know what the telus STBs are.
Anyways, my setup is as follows. I have 1 computer directly plugged into the router. I have my 2 STBs plugged into the router (one of them via coaxial), a ps3, a NAS device, and I have one ethernet going into another wireless N router. The N router is setup as an access point and seamlessely transfers data wired and wirelessly like a switch. I have 5 wireless devices and 1 wired media centre desktop connected to the N router (2 desptops, 2 laptops, 1 wireless printer). However, I also have a wireless G signal coming from the D-link which I use as a back up incase my N router fails.
I have setup all my devices to communicate with each other. Any device connected to any of the routers can connect and access the printer, files off the NAS and Media destop. My ps3 is able to detect and play material off the NAS and media desktop.
UPNP must be enabled on the telus router. Usually it should be enabled by default. If you can give me further insight as to your setup maybe I can help.
I do not know what would happen, if I took out my N router, but I dont think it would be an issue.