I have two Roku's, one LT that come with a lifetime subscription to PlayOn, and an Roku 2XD I bought at Wal-Mart. I have two Tivos, an HD and a Premiere.
My DSL is downloading 2.5 mbps. I sometimes get some buffering, but most of the time it works fine. Can't use two Rokus at the same time because my bandwidth is limited. Although my kids have streamed lower quality Netflix on the Tivo at the same time as I'm on the Roku.
I downloaded PyTivo, a plugin that allows me to record / view my PlayOn stations on the Tivo. The Tivo treats it like a transfer. The PlayOn channels show up at the bottom of the list of recorded shows on the Tivo menu. They are in nested style with menus and sub-menus. I think it was on this forum that I found the PyTivo plugin. PlayOn has Netflix, Hulu, and many other channels.
You won't create any problems by connecting the Roku to your TV, The Roku comes with an HDMI port and an AV RCA style cord / port. You pick which one you want to use. You will have to supply your own HDMI cable. The AV cord comes with the Roku.