Well we've had the roku xs in our house for about two weeks and like it a lot. It's replacing the wii which was primarily used for streaming netflix. It has so many channels but only a select few have been added like mog for playing music (i think you need a subscription after two weeks or something), ted tv, vimeo, twit (which I spent many hours watching FLOSS), classical music, pandora, crackle, and hundreds more. This device exceed my expecattions as to what I thought it could do. I was debating this or the apple tv2 thing but that didn't have rca outputs and we didn't want to have to buy a new tv to watch apple tv. There's a lot of free content on the roku like crackle for movies. The selection isn't be greatest but its uncut, unedited, and free...it says that but there's 15-30 second commercials throughout the movie BUT the movie is paused so it picks right back up. You can sign up for amazon but we haven't done that yet.
I'm sure this is quite similar to the roku orignal but my guess would be the usb port is new on the roku2 so you can plug in a media stick. No, you can't play FLAC or ogg but it could be an easy way to view pictures and ltitle videos. A lot of yall have much better TVs so your images could be displayed on your tv really nicely.
When you first sign up, you will need to register an accout with roku with a credit card (maybe even paypal) and this is in case you want to buy a channel thing. So far we have purchased anything that costs money.
The appletv2 thing looks nice but I also was not crazy about having to sync it to the computer and register it with itunes so while many don't like the roku UI, I think it will improve pretty soon.