-Linksys routers use the same default IP range as the Telus dlink, so you can't plug the Wan port of the router into a lan port on the Telus Dlink unless you change the IP range of one of them (to 168.192.0.x, for example)
-consumer Dlink routers come set to to 0.254 by default so they work fine plugged into a lan port on the Telus Dlink
-Some routers are autodetecting, so if they are assigned a 1.254 address on the wan port, then they'll automatically use a different ip range for their own local network
-Plugging your router wan port into a dlink lan port might work, but the double nat can cause higher pings, so it will sometimes work better to set your router to AP-only mode, or connect lan port to lan port
-The simplest and most reliable method if you want to use your own modem is to use a switch after the VDSL2 modem (not everyone has this modem, people who were hooked up early this year/late last year will only have the Dlink) and plug both customer and telus router wan ports into it
-Running separate networks isn't a long term solution. For example, people using an xBox as an STB won't be able to stream media from their PC to the xBox if they're on separate networks. In the future, the new MS Mediaroom software will allow people to use their STB as Media Center extenders, so you can use your STB to pull up pics/vids/music from your PC.
-Some consumer routers might work fine with Mediaroom. I've seen one customer try with his own dlink router, but the STB couldn't join the multicast stream and froze 10 seconds after each channel change. YMMV.
-It's a good idea to disable the wireless on the dlink if you do run your own router, to reduce the interference.
-There is new firmware being trialed for the dlink that should fix most of the issues - release date unknown.
-There is a new all-in-one VDSL2 modem/router with HCNA, wireless N, and gigabit lan ports, and wifi protected setup, release is very close.
-Telus tech, but my views are my own.