It's a great app, but a few small suggestions:
Nice UI touches, such as the mini-view toggler in the top-left, which makes it really easy to navigate around the map on a mobile device.
Since you can't rotate the map with your fingers, what about it rotating your view point?
I think it would be sensible if the view point snapped back to where the photo was -- it's very easy to place it in a park between two roads and then it's not immediately obvious where the photo is from.
A satellite view would be good, too.
As I'm sure you know, it really needs more image data. I haven't lived in London for years, but it stops a mile from my old school which is frustrating.