Update 2021: sadly, this feature no longer exists.
I have been a fan of moo.com for a long time already. I mainly use postcards and the new luxe postcards. The greatest thing about them: you can have as many different pictures in a set as you have cards in that set and the back of the card can be freely designed, too, by uploading a pdf. Same back of cards for the whole set, which is completely fine – and can be left empty.
Also, the smallest amount of cards per pack is now 10 – so if you want to have different texts on the back of your cards you can do so by ordering packs of 10 cards, one picture per pack.
If anything goes wrong their customer service is excellent.
Use picture enhancement
I think they should have picture enhancement checked as the default, here’s why:
You upload your photos and they look nice on the screen, also on moo’s interface
When you click on the image you can check ‘Photo enhanced, which then shows you a comparison:
But: The preview is not showing you what you’ll get. If you leave Picture enhancement unchecked the products will often look greyish and disappointing. If you check Picture enhancement the products will tend to be a tad too sharp but otherwise the result will be much closer to your original picture.
These are photos of the actual products, the agave is a luxe postcard, the elephant is a standard postcard:
There are cases where Picture enhancement won’t get you what you are looking for, for example if you want part of your picture to stay black. The workaround for this: http://uk.moo.com/help/faq/using-my-own-photos.html
“Remember: where possible, preview your photographs in CMYK. Colours displayed on screen will always look much brighter than the final printed products.
If you have a colour calibrated screen, and would like to preview your images in the same CMYK colourspace MOO uses, we recommend the following settings: Coated FOGRA39.”
As far as I remember you then have to upload the Coated FOGRA39 picture as a PDF so the printer doesn’t change it.