Got one of these the other week from Woot. This does not replace cable in the way I thought it would,but it gets the job done. When looked at the PlayOn.tv channel, I was happy to see ESPN. What I didn't take the time to research was that PlayOn does not give you ESPN without an ESPN account.
The kids love the PBSKids channel because they can watch their favorite shows whenever.
So, this won't replace a traditional cable set up, but it is a lot cheaper and a lot more flexible if you know what you like to watch.
And the iPhone remote rocks. The kids think there is a phantom in the house who keeps changing their channels. Solid.