For in depth technical details, please refer to AnandTech's writeup as mine is just a brief review of my own experience which was somewhat limited in time and scope based on my own needs and curiosities.
I run Windows in a VirtualBox VM at the office but my desktop host only has 4 GB of RAM so I was eager to compare Thin PC to my 64-bit image of Windows 7. The file system foot print was around 2 Gb (including my apps) and it seemed to boot slightly faster but this would probably be better tested on bare metal hardware if you want to get more accurate comparisons.
I installed the Lync chat client, Outlook 2010, and a handful of other small utilities like IrfanView that I use on a semi-regular basis. The apps I did install function just as well as they do on my Win 7 guest OS but one thing I haven't tried is a simple Steam game or one of the games I've bought as part of the Humble Indie Bundle. I'm not sure that's their target market for this product and there's a chance it may not even have much of a life cycle once the slimmed down Windows 8 comes out.
But if your org plans on deploying a Virtual Desktop Infrastructure real soon then this might be worth a look -- especially if you're using deduplication to reduce the storage footprint on the back end. When I have more time I may try to implement Bitlocker or Applocker but my first pass was just a usability test and I'm not using System Center which allegedly makes such things simpler. If you have any experience with these features of Thin PC or have used any current or past iterations of Windows Embedded, I'd be curious to get feedback on your experience.