Flickr users on the iPhone haven't had too hard a time of things. They get a specially optimised version of the website, and the ability to email pictures to upload them, but it's not quite like having a native app to do that kind of stuff for you.
The new app changes all that. Although it doesn't do much beyond what was already possible, it apparently makes the experience much more pleasurable. The main screen is a slideshow of photos from your contacts, and there's an upload button in the top-right corner.
Hitting that takes you to a page where you can name a picture, give it a description, and choose what set to put it in or what tags to give it. You can also choose between privacy settings. The whole experience is much like uploading on the main Flickr website.
Browsing through photos, you can search and thumbnails show up relatively quickly, according to TechCrunch, who've had a play with the app. You can also swipe left and right to move between photos, but there's no pinch-to-zoom option, unfortunately.
The app is available in the app store right now, and it's free.