We love these things! I usually keep one loaded up with a banana in the freezer for a teething day treat. We use the other one for afternoon snack. I actually want to buy a couple more packs so I can keep 2 or 3 in the freezer.
Like one of the other reviewer's said, pears and apples work pretty well. In my experience, a frozen banana seems to clean off a little easier than regular banana.
Some cleaning advice: You have to rinse this thing immediately after use for best cleaning results. It's not a big deal and there's no way around it, but man! This is messy fun for baby! :)