The Beyond Black works really well. It is really liquidy, but a little bit goes a long way. For the money it is pretty cost effective. I've been very impressed with the Surf City products. The Road Grime Destroyer, Beyond Steel Wheel Cleaner and Glass Cleaner are very popular on the detailing forums as well.
I can't really say that I like it more than Opti Gel. I use OG on my personal vehicles, I love the look. The Surf City is very close in looks, it does have a little less gloss. The Surf City does go a lot further, it is very liquidy and spreads on real easy.