We actually have one of the older Roku streaming player models, the HD-XR, and it's a key player in our TV watching setup. Our favorite channels are Netflix and Amazon Instant Video, but there are literally hundreds more to choose from, including Hulu Plus, Pandora, and MLB.tv.
The Roku player isn't as integrated into the Apple content ecosystem as the Apple TV, but I find it to be a more versatile option with many more streaming choices available. The Roku 2 XS even includes an enhanced remote with motion control for gaming!