I came here to say this. I recently built a pretty tight integration between Trello and our app, and using the API was quite pleasant. The documentation isn't stellar (it has examples for requests, but not responses, s you need to use trial and error), but everything is standardized, so once you figure out the logic, you're golden.
I actually found Trello's API to be one of the worst most non-compliant restful API's I've seen. Nothing about it is restful with the extra actions they have on resources. It's hard to follow. The docs are sub-par too.
I interviewed with Trello and one part of my interview was building a super simple app in an hour using their API. As far as APIs go, and never having used Trello's API before, I found it to be fairly intuitive and documented well enough for me to skim quickly to needed information. I completed the task with time to spare, and only choked a bit on the authentication. If you don't like Trello's API, give the AWS API a shot!
