Now that we see a quite large amount of OS X Lion questions here on Super User, I've seen people telling the OP to go to ask on Ask Different.

Of course, the folks at Ask Different want their site promoted:

Now that Lion is out, help promote Ask Different!

Now that Lion is shipping, there will be zillions of mac users upgrading, and they'll have lots of questions. And since all those questions will be new, Ask Different will have as good a shot at having the best answer than any of those, you know, competitive sites. Essentially, this is a great time to recruit new members!

And it seems there are people who dislike having so many OS X questions on Super User. Still, questions about OS X are on topic here.

Is it therefore justified to inform people (who suggest to go to Ask Different) that Mac hardware and OS X questions are perfectly on-topic here and should not be migrated or closed?

This probably is the reason why there is no migration path to Ask Different yet.

_{Further discussion: I've added an answer to the above meta.Apple.SE question. Joel Spolsky then added a comment that I should bring it up here, so I did. So what do you think? Should we give Ask Different more users by telling them to go elsewhere? Basically like having ads for Ask Ubuntu. Is anybody annoyed by having so many recent OS X questions?}

_{I would think that it's fine to tell the OP about Ask Different in the case of a very specific question that hasn't yet received an answer. But then again we shouldn't encourage people to cross-post.}