The SlingBox looks cool, but GOODNESS is it expensive!
I just have a Miglia TVMicro, and have the cable split, one for my computer, another for the TV. Obviously, my computer only gets standard cable channels.
However, if I plug the cable direct from the box to my TVMicro, I can record anything I want, but it has to be tuned at the box and not my computer.
If you're looking for a cheap(er) solution, I'd recommend it.
EDIT: You said you wanted to watch, nothing about recording, so this is probably worth disregarding.