We've mentioned Flickery a couple of times, and I've been using it for over a year now as my desktop client for Flickr. Developer Matthias Gansrigler has added quite a few new features since the last time we covered it, and the performance has increased significantly.
Now that Flickery is available in the Mac App Store (US$23.99), that's going to be the exclusive outlet for new customers. Updates for current users will still be delivered outside of the App Store, though.
If you're a Flickr user, I'd recommend taking a look at Flickery. In fact, we have three Mac App Store promo code
