With Angie's List, be wary of jumping on companies at the top of search results. Consumer Reports found that businesses with "A" or "B" ratings that also pay for advertising rise to the top of default search results. It's a big advantage.
Consumer Reports Money Adviser also checked out other rating services, including Yelp and Google Plus Local. Google Plus Local didn't respond when asked how it verifies that its reviews are from real customers. Yelp told Consumer Reports that they have a way to identify and delete bogus reviews but admitted that the system has not been objectively tested. Yelp also allows businesses to buy their way to the top of the pack in search results. But unlike Angie's List, Yelp clearly labels the ad.
Consumer Reports found that ratings for the same business can vary significantly from site to site. But if you can't get a recommendation from someone you know, it may be worth it to look up a business on several sites.
In most communities Angie's List charges subscribers to sign up. Yelp and Google Plus Local are free. Another free service that Consumer Reports says is worth checking is the nonprofit Better Business Bureau. It deals with complaints against companies and rates them on how well they resolve the problems.