Another thing to consider is the reputation of the company you are dealing with. This is a tough one to sleuth out, though. If you do a search on google for most any major company that sells products, you'll find a disgruntled customer bashing them, or maybe even claiming that the company is run by the devil himself!
Here are a few ways to get accurate information on the company – the best way is through the Better business Bureau. The better business bureau processes customer complaints and creates reports on each company based on the complaints received. The Bureau analyzes each complaint, though, and marks invalid complaints and complaints that the company resolved, and/or made a good effort to resolve. So the better business bureau is a good source for accurate information on the business practices of companies.
Another place to get customer feedback on companies is Alexa. They allow customers to write reviews on websites. Keep in mind, you will find a lot of people just bashing other companies on Alexa, so try to be selective in which reviews to place much trust in.
Another way to check out a product is to do “testimonial checks”. Most companies will have product testimonials which they use to promote their product. However, many of these are fabricated testimonials. So, just ask to speak with several references. It's harder to fabricate real people!
Just as many companies use testimonials, many use medical references, generally doctors who recommend the product. It's not a bad idea to check and see if the doctors are actually practicing MD's who use and recommend the product, or if they are just employees of the company who are paid to recommend it. Of course, just because they are paid to recommend it doesn't mean it's not a good product, but it will lessen the weight of their recommendation.