I have been using Fastprinting for all of my marketing materials for over a year.
Their service, prices and product quality are all amazing. Their turnaround time is always reasonable (if not fantastically fast). I've ordered business cards, post cards, custom sized cards in 2 different sizes, custom sized single page prints, poster prints and most recently my vinyl stickers. All of these products are amazing. The print quality and paper quality are fantastic.
I have never had anything close to a negative experience with them, and if I ever do, I'm sure they'd rectify it as quickly as possible.
I love Fastprinting and I'll be a loyal customer for years to come.