If you prefer to keep C-stick as smashes, you can still perform PDC Dtilts by doing the following:
1) Dash right
2) Turn around by holding down-left
3) C-stick down
The result is that you get the same turn around animation with the C-stick doing a Dtilt instead of a Dsmash.
Also, if you turn off Tap Jump, you can do Utilts similarly (just replace "down" with "up" in the directions above).
I haven't been able to figure out the pivot grab thing that was mentioned earlier, though.
EDIT:
Also, if you have a projectile to throw (like a bomb, grenade, turnip, banana peel, etc.), you can throw the projectile during the sliding animation. For instance, with Toon Link holding a bomb, you can dash right, hold left, and C-stick throw the bomb to the right while you slide to the left. Kind of a "glide toss" effect.
Another possible use of the DPC is to position yourself such that a particular part of your character's Dsmash hits the opponent. In other words, you could run past your opponent, and DPC into a Dsmash such that the first hit of the Dsmash hits your opponent (if your Dsmash hits in front first).
Or if you have a character whose Dsmash hits behind first, you can possibly run right up to someone and DPC such that the back part of your Dsmash hits.