We take our aussie to a dog park occasionally and she really loves it. I see the same people there every time and it's kind of a little community. I think that keeps it pretty honest for the most part. I think about things like her picking up illnesses but, honestly, parvo for instance can be anywhere and she's just as likely to pick it up running around with dogs here in the neighborhood,w hich always happens while we're walking because we live in a tiny little town where everyone knows everyone.
Other than that though, go check one out and see if you like it. I was really worried at first but I can't imagine not taking her now.