I have purchased stuff from there. Several shirts and some shoes back when they used to do them (I think it was zazzle where I got the shoes from anyways). Oh, and I bought some envelopes, which are absolutely awesome. I would totally buy envelopes again, I just wish there were writing paper options too, rather than just cards. I've had no issues with anything. Sometimes the things seem way to expensive, especially considering the end quality is a bit low. But the sizes are good, and if you don't like the style offered you usually have to option to change it, which is great.
I did have a store once, for Pony Fair Australia merchandise. But we had hasbro ponies in the logo for Pony Fair, and they didn't let us print anything with them on it. Boo!