Seems everyone wants this feature for large-scale RPGs and such but I question how it benefits them at all. Maybe I'm missing something, but for a large project you'll need complete and total control over every aspect of your saved data which isn't what you're getting with save states. Plus if you're loading levels externally, which you probably should for said projects, then they're useless.
For complex subscreens and such you want contained in separate layouts, however, this is a godsend. You could save state, go to said layout, return to the original, and pick up where you left off. That said, I'm looking forward to this feature :)