I bought this device about a week ago, and at first, I wasn't too impressed.
Lets start with the main reason many people will buy this device, Media Streaming. When I connected it to my network, It refused to play media from my PC running PS3 media server (which works fine with my PS3, Xbox, WDTV Live.) I receieved the error alot of reviews mention, not being able to stream movies. After looking around the internet, I found one suggestion to try some software called Serviio. After installing this on my PC, and waiting a couple of hours for my Media files to cache, the device worked without a hitch, and is actually much better than PS3 Media Server. It lets you not only view all your movies and TV shows in a directory but also sort them by actor, director, and many more. If you get this device, make sure you get Serviio (its free!).
Secondly, the internet TV features. Very good I thought, It has YouTube, Love Film, Sky News, iPlayer, and a good few more, including speciality stuff like extreme sports. All of the Apps run very well & quickly.
One problem using a couple of the apps is the fact you don't have a keyboard, but fear not! Sony has very nicely produced a free app for touchscreen devices (tested on my iPhone/iPad). Which lets you not only control your Media Player over the network by swiping to navigate menus but also lets you use an onscreen keyboard. Brilliant for YouTube.
All in all, I am now impressed with this device, but it would be worthless without Serviio, thank god I found it. I hope this solves the streaming issues for everyone who reads this.
(P.s. BestBuy now price match Amazon, so if you go instore, you can get it cheaper than here!)