I've been using a Hebie Chainglider for almost a year now. (It's been on two different singlespeeds, not with a gearhub.) I love it, both because it keeps my chain cleaner and because I don't have to worry about getting chaingrease on anything. I really miss it when I have to pick and carry other bikes.
The biggest limitation with the Chainglider is the limited number of ratios each model fits — each fits one of three chainrings and a range of a few spocket sizes — but if your ratio works, then no problem.
I have it on my Kogswell now: http://flickr.com/photos/a/tags/chainglider/