1) It streams, just streams. No free cable, no live feeds of "The Tonight Show", no nothing else.
2) It streams many, many more things than your internet TV, your Blu-Ray player, your Wii.
3) This one has 1080p capability and wired, as well as wireless, connectivity.
After recommending Roku to others for a long time, I bought two last week. Installed one in ten minutes, via wired connection, and stream to my 1080p television. Perfect.
Added a few private channels yesterday, including BBC World news and Al Jazeera. Still have room for Glenn Beck TV, though, I guess.