There was a recent story in the NY times about an online retailer who purposely treated his customers badly to get negative reviews. It turns out those online reviews bad or good, helps raise the companies search engine rankings for the products it sold. The owner of the company admitted that he treated his customers badly because he knows that an outraged customer will go someone on the internet and give him a bad review.   He discovered that in terms of rankings, bad reviews were just as good as good reviews and it was a lot easier to get customers to take the time to do a bad review if you treated them poorly enough.
Google has since changed its ranking algorithm to correct this issue.   Getting good reviews however will continue to enhance rankings, and in many cases is vital to get good rankings.   Getting customer reviews is important, Google pays attention to them and they don’t necessarily have to create a link to your to help your site ranking. 
There are lots of places that you can get customer reviews that will help your local ranking as well as your organic ranking.   Google Maps, Yahoo Local Directory, Yelps, Judy’s Book, City Pages, City Search most yellow page listings are just some of the places where we know that reviews get noticed by Google.   Even if you are not a “local” business, it is a good idea to ask your customers to give you reviews on some of these sites.   Getting reviews or testimonials on your own site will help, but I don’t think that it carries as much weight as the other sites mentioned.  
There are also services that will help you solicit reviews from your customers and publish them on review sites.   These reviews seem to be gaining favor with the search engines and many of these services are very reasonably priced. If interested just let me know and we can get you on a customer review program.   In summary, every business should have an ongoing program (or process) to solicit and publish reviews about you.