Just to add my newbie 2 cents, I have had 7X5's, 8X12's, 20X30's, Panos and even several of their photo books and was very pleased with the turn around and the quality. I even had a few extra prints thrown in on the large ones as the said they had run some 'Control' prints and sent them to me for free.
Also, you can set up what they call a pro gallery where you can add a markup to prints if you want to consider selling them!!
Also 2, you can send a link to somebody and they can choose their own pictures to print and have them sent direct. Pretty cool really!
(no I dont work for photobox!!)