What is the purpose of waffle irons that flip? I saw some local shops selling waffle irons that have a complicated gimbal mechanism (such as the Bella Rotating Waffle Maker listed here). What is the purpose of begin able to turn the waffle within this device? Does this have any advantage over a regular waffle iron that just has a top lid that opens?
Some waffle irons flip to evenly spread the batter. This is important in commercial applications where the visual presentation of the product is crucial and can save on batter - you can use less batter to get a thick, complete waffle. 

The waffle iron presses rely on the expansion of the batter to create a complete waffle. Sometimes in order to get a full, thick waffle, you have to use a little more batter, which often ends up spilling over to the side. It's a trade-off - if you don't want spills, use less batter with the potential for a slightly incomplete waffle.'

From eBay's Waffle Maker Buying Guide - "This ensures even cooking, and it ensures that batter is evenly distributed. There's less risk of ending up with a waffle that has holes."