Haven't been to DLP yet, so I've never experienced it, but it's similar to a film version of the Great Movie Ride, and it's an exclusive. I'd try it out. My personal itinerary would be:
Ratatouille
Crush's Coaster
Toy Story Land (Slinky Dog, RC Raer, Parachute Drop)
Mickey and the Magician (NEW live show)
The Art of Disney Animation (just a quick walkthrough to check things out)
CineMagique
Studio Tram Tour: Behind the Magic (weak, I'm sure, but just to reminisce)
second tier:
The Twilight Zone Tower of Terror & Rock 'n' Roller Coaster (for the fun, in case you have time. But unless the wait times for these are low, I'd make sure to try the exclusives first)
Cars Race Rally
EDIT: I just read you meant one day in DLP, not WDS alone. I'm not really sure then.. lol.