My husband and I were looking for a mattress at the mattress retailers with beds costing a lot more that we wanted to pay.  We were about to fork over the cash for one when someone told us to buy it online.  The prices were so agreeable that if it didn't work out we didn't care if it only lasted a year.  It was worth the risk  
We have had our bed for 6 months now and love it.  I have had great sleep on it.  My husband is picky about his comfort and would buy a mattress in a box again.  

Pros: great value, comfortable