Pro accounts are being phased out, but existing Pro users get to keep their unlimited space, ad-free browsing, and statistics (for now). In place of Pro accounts, Flickr is now offering paid upgrades for either going ad-free ($50/year) or doubling your space to 2TB ($500/year).
The revamped UI takes cues from other social platforms like Twitter, App.net, Facebook, Google+, and Path, in that it allows you to upload a cover photo and displays your profile in a similar manner to those services. It's not wholly original or anything but I think it looks great. At least it doesn't look like 2006 anymore.
Photo pages are also much nicer, with images displayed in full resolution and shoving all the related info (description, comments, etc) below. It gives the photos a chance to breathe, which I love.
I need more time to play with this new interface, but I'm already really liking it so far. Kudos to Marissa Mayer and the Flickr team for shipping such a fantastic update.
Here is my Flickr page if you'd like to check it out.