First, a disclaimer: I am all about the Alien from Toy Story. When I saw they had a Pizza Planet, I knew I had to eat there (only been to WDW once, for my honeymoon); when I saw in pictures that they had the aliens hanging from the ceiling, it was sealed.
Then...I got there. If you are really into Toy Story, the restaurant itself is a huge disappointment, theming-wise. Sure, there are some arcade games (none really good), but the place looks nothing like Pizza Planet from the movie - it looks like a converted warehouse of some sort. The aliens hanging from the ceiling, look decent in pictures, but up close are really.....odd. It looks like they've been stretched, and sort of like their head is disconnected from the body. Fairly creepy. Also, as a fan of Toy Story (and again, specifically the alien), I found the lack of a rocket-shaped crane machine filled with aliens a huge letdown. It would be so easy for Disney to pull this off, it being the centerpiece of the experience at Pizza Planet from the movie, but again, nothing.
The pizza is the exact same stuff you get at the resorts, Pizzafari, etc. Basically a thick crust with some thin sauce slathered on top and a tiny bit of cheese/pepperoni - not any better in quality than a DiGiorno at best.
Overall: I was highly disappointed and walked out without having eaten there, having already experienced the pizza at our resort and Pizzafari (and knowing exactly what to expect of it). I think with a little bit of attention by Disney, Pizza Planet would have the ability to be an excellent restaurant and an attraction in and of itself, but it would certainly take a refurbishment and some theming to make it so. As others said, if you are just looking for a place to eat - the pizza won't kill you, but don't expect it to be any kind of great experience, either from the food or the theming.