The main view was completely redesigned: the category buttons are now smaller, the Featured category was moved to the bottom and it doesn't have the next/previous buttons anymore. However, the Featured applications category still has the nice autoscroll feature it got a while back.
The category and subcategory views were also updated and the double pane view was removed. Also, a new category called "What's New" was created - this will be the category where the new applications from the extras.ubuntu.com repository we were telling you about will be available.
This is how Ubuntu Software Center used to look about 2 weeks ago:
The new Ubuntu Software Center version (2.1.4) also feels a lot faster!
Want to try out the latest Ubuntu Software Center 2.1.4 in Lucid? We could have build it in a PPA but that takes too long for something so trivial, so you can simply download a .deb package (you'll also need these dependencies: aptdaemon, python-aptdaemon-gtk and python-aptdaemon) - all debs work for both 32bit and 64bit - and install it.
The package will also probably be available in the guido-iodice PPA later today.