We replaced our Bluecoat system with the Web Gateway 7 system about one year ago and are bery happy with it.
Administration is much easier. We are now able to filter HTTPS sites as well so overall we are much more secure.
Constant updates, antivirus scanner, and customer support are some of the reasons to choose the Web Gateway.
Plus the many different kinds of deployment options is another reason.
Former bluecoat administrator here and now at this job just implented MWG 7. My first thoughts was BlueCoat was much better than MWG6, but when 7 came out I really think it evened out the playing field. 7's interface is pretty easy to use, things are laid out pretty nicely, performance is good, and appreciate the top-down rule approach as opposed to the layered tabs in BlueCoat. That being said, there is a lot where 7 can improve on and I've posted that in some previous posts. I think BlueCoat excels with their troubleshooting files, documentation and they seemed to handle streaming media sites much better than MWG 7. The MWG price is right and overall happy with the product so far.