Have you ever bought a domain from a parking service?

I'm curious if anyone has experience purchasing a domain name from one of those services that buy up the good ones from the cheap providers and resells them at a higher cost. If you do, what was it like? Are they shady? What kind of price could I expect?

I'm hesitant to give any information to any of them for fear of getting a bunch of spam. I'm looking at http://pl.sh/ and http://poli.sh/ for a possible custom shortened URL for polished.

What are your thoughts? How would you go about inquiring about something like this?