Clickview is a great teaching tool, not only can it serve video files, in a network friendly way, it can give access to resources specific to certain videos, create lesson plans involving videos, audio, images and documents.
There are a vast array of videos available through the exchange, and media store. It might not be the best fit for all schools but if you have a large collection of video resources its definitely worth at least a look.
The hardware can be a bit pricey for what it does, the 24/7 and live boxes are very useful but not worth the cash in my opinion.
The whole thing is designed for schools, so from a teacher POV its great, easy to use, search and can even edit and export videos for use on VLE's and powerpoint presentations. Also finally, the support i've had from ClickView has been beyond brilliant.