While I agree with you on most of what you've said, I feel I have to defend Yahoo on a couple of points. First of all, the basic page interface is all that you said it is in terms of layout and clutter...yet when you use the api to generate your own Yahoo map on a page you can make it as sparse as you want it to be. And jeez o petes, the API is simply overwhelming in its attempt to be complete and flexible and versatile. There's a lot of depth to be discovered here...and on a certain level, the point of entry is way easier than Google's API was (although, admittedly, I learned from Google valuable skills I can now apply toward Yahoo. And clearly, they've learned a lot from Google's experience.
But yeah, there's a certain elegance that isn't here...and surprisingly, some of it comes from using Flash (the zooming in and out until it's pixely and then loading the new tiles...eh, don't like that much. The basic idea of "as much UI as you need, and not a bit more" is certainly absent.