For those of you looking for a media center or media center extender device, the Mvix is a great alternative to the Apple TV. I tested out the Mvix MX-760HD a couple of weeks ago. The Mvix is about the size of a large external hard drive. It does not ship with an hard drive, but you can install one if you choose. Installation requires removing thumbscrews, and popping in the drive. The fit is a little tight, but it works.
Regardless of whether you install a hard drive, the device can stream many kinds of data from your network. The Mvix handled every type of file I tried, including VOB files. However, it cannot play protected content. I did experience some stutter in video playback with large, DVD-sized files while streaming video wirelessly. For the most part, video playback was quite good.
If you do chose to install a hard drive, you can hook up the drive to your computer and drag and drop files. If you are sharing video from a Mac, you will want to use something like SharePoints to allow the Mvix to access the files. If you choose to get the Mvix, take a look over at OReillyNet.com for an excellent article about how to hook up an Mvix to your Mac network.
Hooking the Mvix up to a television was a snap. The Mvix has composite out (for older televisions), S-Video out, component out, and DVI out. It supports resolutions up to 1080P (the Apple TV tops out at 720P).
The device itself is not as stylish as an Apple TV, but it is far from ugly. The interface is not as snazzy as an Apple TV, but if you can live without the flashiness, the Mvix is a quite capable machine. It costs $299 over at ThinkGeek.