I've been playing a bit on this site recently:
The graphics are horrible.
It works even if your computer is behind a firewall. This is because if it fails to connect in the usual way (using a port? I'm not really very computer literate) it uses some sort of HTML protocol to exchange moves. This is quite slow, I reckon I get about 75% of the time I would have in game on playchess.com with the same time control. And the graphics are horrible, which means it takes a little longer to work out the position.
Anyway, it's something a bit different to the usual online chess sites.
Did I mention the graphics? They're horrible.