We stayed there in Feb 2012 and had a great time! We had already spent a few days in Honolulu, and driving around the island, so didn't feel the need to go offsite at all while at Aulani.The food choices onsite were very expensive though, so we made some notes while there, on ways to save a bit if/when we ever get back again.
We thought the best bargain onsite was the bar by the pool - it was very pleasant to have lunch under the umbrellas overlooking the pool area, and the prices weren't too bad.
The kitchens are so nicely equpped that we also thought that it would be smart to stop at Costco and/or
Walmart on the way up, and get some meat and/or fish to grill (they were putting in bbq's while we were there), and some rice to fix in the rice cooker, some fruits & juices to make smoothies in the blender, and some lunch picnic foods. There are some really nice picnic spots if you walk just a ways down the beach from the resort, and I could see packing some rolls, ham, cheese, fruit, etc. and taking a nice walk down the beach for a picnic.
Also, you probably already know this since you've been to Hawaii before, but be sure to ask the locals where the best plate lunch places are - plate lunches are best bargain in the islands!
Have a great time! Aloha!