Here's some info:
http://www.sportsbookreview.com/SR.aspx?s=ehorse
I'm not sure this one is unbiased!
http://www.youtube.com/watch?v=wyrqmBevAv8
Old review:
http://www.sportsgamblingreview.com/ehorse.htm
Voodoo: I've heard nothing negative about Ehorse and some positives. EhorseX, their betting exchange, I think is a tough way to go - they have some sharp dudes that wait to hammer you at the last minute so I would stay away from EhorseX. I think Ehorse has been around since 1999 and is Costa Rican based. They book their own bets so I guess if you were tremendously successful, they might not care for it.