Latest results on the poll are a bit more encouraging. No one admits to having played the game (which sucks) but "No, but I really want to!" has 9 votes, beating the flat "No", which only got 5.
If you want to do a classic "Wandering Adventurers" campaign, that is totally doable (Just ask Woot) and there are tons of adventure seeds and ideas in the rulebook to support that. But what if you want to explore a single area in depth? That's when we start talking sandbox (or pinball, to use my preferred metaphor).
If you wanted to create a sandbox of original creations, both the Munchkin and Gillikin countries have plenty of unexplored space to put whatever you want. Or you could take advantage of the well-documented Quadling Country. The Emerald City is also a great setting for a campaign; Not only does it have immense variety within itself, but it can also lead to a variety of adventures in Oz at large.
The hard part about building a pinball machine from existing Oz material is that many of the countries exist by themselves, with no real relations to their neighbors. In fact some, like the Cuttenclip Village and Bunnybury, are strongly isolationist in order to protect their citizens. But there are some that can clearly benefit from connecting to other communities. For example, Bunbury and Utensia. Bunbury is populated by living baked goods, while the people of Utensia are living kitchen utensils. Perhaps, when a boy Bunn and a girl Bunn love each other very much, they take a trip over to Utensia. After much preparation, they are finally ready to put their little baby Bunn in the oven to be properly baked.
Suddenly, new adventures present themselves. What if Mayor Cinnamon Bunn's son fell in love with the daughter of his enemy, Herr Kaiser Roll and the lovebuns are dashing away to a honeymoon in Utensia? Worse yet, what if, in their hurry, they get terribly lost and head toward the Forest of Fighting Trees? Now, on top of the challenge of locating the lost couple, your players have to keep them from getting smashed into crumbs by the Fighting Trees.
Creating these sorts of connections will give your players plenty of pins and bumpers for their characters to bounce off of into all sorts of directions.