We use more than 400 NComputing L300s in an FE College as part of a fleet of 1600 PCs. The supplier is http://www.axesssystems.co.uk/ who we buy the hardware from and if you get in touch Im sure they will provide reference sites.
Generally the L300 is great for the price, obviously the performance is directly related to the hardware you run as the server, so the requirements are very similar to the specs you would need when settiing up an RDS server. As an example, we typically get around 40 users comfortably running on Core i7 with 32gb ram with 3 7200rpm drives in RAID0. Comfortably as in they are much faster than many of our desktop machines.
Video playback on websites is good, not amazing. There is a setting to enable or disable video playback, with it disabled you'll get bad tearing. Enabled, its only really any good in Google Chrome as Internet Explorer tends to behave a bit odd, with some sites the whole screen becomes distorted and unreadable. Solution is to turn off video playback or use Google Chrome as the browser which works great.
USB support is the downfall, although they are sold as being able to support USB storage the reliability is hit and miss, some days it works other days the same USB stick will not work until the server gets rebooted. Isochronous USB devices like Webcams, scanners, etc will not work at all and NComputing are up front about this in their specs.
