I mainly use BBTS and Robotkingdom, occasionally I use AmiAmi through a friend who does a lot of his orders through there, so we can take advantage of discounts through bulk shipping.

As others have said, BBTS and Robotkingdom have very good customer service, I've never had a problem with them yet. Whenever there have been QC issues with figures they have been quick to respond and provide replacement parts or offer store credits. And the POL option with BBTS is a great way to save money on shipping.