Ask HN: Has anyone used the Yelp API?

I am in the process of building a local restaurant guide and was hoping to use the Yelp API to help augment the information I already have. It would seem that the terms of use (http://www.yelp.com/developers/getting_started/api_terms) restricts you from doing anything interesting with their data. I had hoped to aggregate their ratings with other review sites, including my own, and also to cache these ratings locally as I am not shooting for "real-time" results. Does anyone know how aggressively Yelp polices the usage of their API? Has anyone made anything useful with this API and the restrictions in place?