I needed to get some business cards to hand out at various times and decided to try the Flickr / Moo option. I have a Flickr site and read the specifications for sizing photos as Moo cards and made 10 card designs in Photoshop. I got the Moo 100 card pack for approximately $20 and it took about 10 days to arrive from the UK. The cards come in a little plastic holder which is nice. Click the photo below to see a larger version for more detail.
The cards turned out well and the paper is heavier than regular photo paper. They feel solid like a typical business card and have a matte/satin photo on one side and my name, email, and web site link on the back. I think the price and the ability to custom design up to 100 different types of cards is worthwhile.
The one thing I would do differently next time is to adjust the photos to make the images and text contrast more. For example, I used grey instead of pure white for the text on the photo and the grey at that size is a little difficult to read. However, they turned out great and should work just fine for my current purposes.