Personally I like Yelp and use it to find restaurants in metro areas - that is Yelp's sweet spot.
Things to think about:
1) You can't edit, moderate, remove or comment on reviews. They are posted immediately and they are permanent.
2) Customers can post their Yelp review to their person FB page. This is great if the review is positive.
3) You can use it free.
4) They get picked up by Google but their have been issues between Google and Yelp.
5) Yelp has proprietary filters to try to screen out fake reviews of which their are many which can cause reviews to disappear. They try to rate the reviewer which favors reviewers with many post.