If you haven’t seen Photosynth, check out Trg Ban Jelacic in Zagreb, Croatia on Bing. There are a lot of great interaction mechanisms in Photosynth. Among them, you can click right where you want to look, there are lighter-colored and related images close to the current one so you feel the context of the image, and the angled, 3-d jumps you into the scene. Zagreb feels just like that.
I’m not in the habit of being negative on this blog, but there is one thing I think Photosynth could really benefit from: a feature that emulates the taste of a cappuccino from a cafe on the square.