Haha, it's impossible to print in iOS. iOS is so locked down, you can't do anything that's real productive in there. The only reason iOS is so popular is because of the apple brand and Apple has spent a billion dollars training people to think of tablets as for fun and games only.
I'm a field engineer managing constructions. We used to have to carry very large 3,000+ page documents around with us for references. Every agency has their own rules and regulations. Nowadays, I just carry around my windows tablet. The other engineers are catching up. They're doing the same thing. But when other people look at us, they just assume we're carrying those tablets around for fun and games. Because of Apple's campaign against mobile productivity, people can't imagine a tablet being good for anything else but fun and games.
Android is better because you can "share" your documents with something like printer-share. There used to be a lack of drivers for the printer-share app. It's a lot better now. I haven't had a problem with it. so, when I want my android app to print, all I gotta do is add a share feature to it and the user can point it to printer-share. Simple.
Windows 8 metro is, of course, the most complete. But again, it is so complete that the development behind the apps are geared toward large companies while leaving indie devs like myself out in the cold. That's why indie devs are hesitating to come over to windows 8 development. MS needs to realize that if they want more quality apps in the winstore and not just crap-apps, they need to make it easier for us indie devs to write out quality apps for them. And making the print protocol 200+ lines long is not easier.
Per bolded, that reminds me of a very critical editorial against Surface. The argument was that "tablets are for media consumption, duh." ...Uh, because previous tablets were not created for productivity, ergo that's all they were good for, but that doesn't mean tablets can't be manufactured for productivity in various sectors. (That was a pretty stupid author.)
According to this article, you can print from any Metro app using the charm. That sounds like an end-user solution; does there really have to be a lot of dev intervention?