I've had two pairs of the eBay chinese wheels; one 38MM and the other 50MM in rim brake. Here's my anecdotal review.
For ~$350, they're a decent deal and are really what's expected for that price. I've taken them on some good climbs/descents but there's a lack of trust in them; particularly in the braking performance. However pulling the hubs apart, you can see the lack of precision in the manufacturing process. My main complaint is that they don't roll well; there always seems to be a drag or roughness to the bearings and hubs. I put some new bearings into the 50MM but they still don't ride as smooth as my alloy wheels (Cero AR30).
IMHO I'd put the money towards a nice set of alloy wheels or save up for carbon wheels from an established brand.