Flickr's got a new do! As a heavy Flickr user I appreciate the updated UI. It's been years since Yahoo! has done anything interesting with the web version, even after launching the iOS app they have barely touched the look or functionality of the main site.
Like Facebook, Google+, and Twitter, Flickr has added a profile page with a high resolution avatar on the left inside a horizontal banner photo. It's everywhere these days, but for Flickr I think it really works, especially when you choose a banner photo that works well within the narrow banner.
The old photostream layout looked far cleaner if all your photos are the same aspect ratio. I rarely posted portrait oriented photos because they looked awkward almongst mostly landscapes, but with the new grid look I anticipate this will be less of an issue.
Flickr is obviously targetting the smartphone, particularly iPhone, market. It's not surprising given that the iPhone is the most popular camera used by Flickr users. Personally I never use the app for taking photos, so any shoot and edit functionality is lost on me. I do however use the app quite frequently for review my own photos, and exploring other users photos.
I appreciate the mix of users, serious photographers, casual photographers, smartphone and social media users, and visual art aficionados.