Beepster
I'd imagine for loop based producers that deal with a lot of Groove Clips in the Track View it would be useful.
It's also incredibly useful for audio for video, where you're moving clips around
en masse, but then need to zoom way in and snap precisely to an event in the video - where you've used either time compression/expansion or tempo changes so that the event happens right on the beat.
But of course, the beauty of Smart Grid - like so many other features in SONAR - is you don't have to be a victim and imagine that it's doing nasty things to you.
You decide whether you want to use it or not, and act accordingly.