Last year, I bought a Chugger Pump (chuggerpump.com) and have used it without problem until a few weeks ago when it stopped working. I called up customer service at Chugger Pump and they promptly gave me an RMA and asked to send it in. Within a few days, they had contacted me via email with what the problem was (turned out some gunk had gotten into the pump housing) and promptly sent me a new replacement. They had just released a new upgraded pump as well and were having a sale on them, so I bought an extra.
Can't say enough about their customer support - I highly recommend Chugger pumps and their company.