The official Flickr app for Windows Phone 7 has just been upgraded to Mango, and now features pretty good Windows Phone 7 integration.
The app now integrates with the Camera app, allowing one to share pictures directly from there. It also has its own built-in camera app with a grid overlay allowing for perfect composition and direct upload to Flickr. The camera app can also be pinned directly to the start screen, as can the activity of contacts. The app unfortunately still lacks the ability to pin groups to the start screen.
Scrolling is still not as smooth as one would like, but this may just be the nature of the off-site data.
Flickr for Windows phone 7.5 can be found in Marketplace here.
Thanks Phillip and Gae for the tip.