From what I've seen, they are just cheap sunglasses. Nothing too special about them. If you want something nice, and Rx compatible, but not crazy expensive check out Ryders. They make 2 different styles of glasses with their "gasket" technology. The gasket allows you to make a Rx lens for the glasses, and not even have to use inserts!
The problem with most sports glasses is that they have an 8 base curve to them, which is very difficult to make a lens for. The gasket for Ryders allows the lenses to only have a 6 base curve, which optitricians (sp?) can make a lens for, but still fit in the frame with an 8 base curve. They look awesome, and doesn't look out of place at all!
Check out Ryders at:
Check out the Coilers
Check out the Freefall
Both the Coiler and Freefall use that gasket technology. If you want additional lenses with the gaskets (essentially blanks for you optitrician) they are $15 for clear, $20 for orange, and $30 for tinted.
Hope that helps! The fact that they are not just inserts will make them a lot more comfortable, and fit a lot better!