It's interesting but on a simple level I find myself working with JSF in a whole new way via Seam. I guess it was just such a pain in the ass to add managed beans to the config file that I kept my beans to a minimum. With Seam, however, I find that my beans end up being far more granular in their purposes (not to mention the added scopes + injection helping in the granularity!). I have a ton more objects than I would otherwise, but the application as a whole makes a lot more sense!
That's a great benefit, I think as inherent with JSF on it's own, you have the option to scale as you please. Seam does a great job of carrying that layer back into much lower levels (persistence) if you choose.