I have this very same question. I'm coming from the Windows world, where I was happy with MS Publisher (price and features).
The iStudio website has some incredible examples, and it has some functionality that doesn't exist in MS Publisher, and as far as I can tell, Pages. Pages is cheaper, easier to use, but a lot less functionality. I guess it just depends on what you want to do with it.
If you have some experience with DTP and are looking for a more fully-featured software then try Pagestream. I have used in previously on Amiga, PC and now Mac. It doesn't have the quick and easy to use templates for beginner or occasional use, but after some learning can produce very precise and professional documents.