I've made 2 purchases and so far the cards have been perfect. My only issue is the long production time, but that's not at all a big deal as long as I can inform my client ahead of time. The cards were fantastic and my clients were very pleased.
Whenever using any outside vendor, we always thoroughly preflight our files and are sure to send hi-res PDF files with crops & bleeds. As the content creator, it's our responsibility to be sure the files we send are 100% perfect.