I wonder if it'll be available in the UK. Hopefully! I say "hopefully" because attempting to upload photos from my wife's iPad to photobox-like websites is incredibly painful or impossible (or you must use their app due to the iPad having no filesystem access, where ordinary file-access HTML elements just appear as blank spaces in forms, making it IMPOSSIBLE to upload from a website, thereby forcing you to install some rubbish crippled app).
Apple's competitive relative to something like Blurb (which is the on-demand printing provider built into Lightroom)... maybe even a little cheaper for a similar product.
They're more expensive than (for example) Walgreens, but, without ordering books from both, I'm not sure if they're similar quality-wise.