Re: What to look for when buying used pedals...
Just inspect any metal plates/hinges/cast parts for cracks or excessive wear. Those are the only real things you need to worry about, since virtually every other piece of the pedal is easily replacable. That, and check to make sure none of the little threads on the cam or anything are stripped, or excessively worn.
I got a DW5002 used a few years ago for $150. I never use the slave pedal, but as a single pedal, it's still going strong. The only thing I've had to replace is the spring. As a rule, I always buy drum gear used if I can find it.
It's probably a good idea to put the spring from your current pedal onto the pedal that you're trying out, so that you know if the pedal lacks response, or just has a weak spring.