So the Apps UI has been completely overhauled, three steps forward, two steps back. Installed apps are now listed in alpha order rather than randomly as was the case before--good. Clicking on an installed app brings up information about that app--good.
"Available" being renamed to "Discover" seems unintuitive, though that may be because I was used to Available. Categorizing the apps seems like a good step, though some of the categories--and the apps assigned to them--seem kind of arbitrary.
But the big fail here is the design of the Discover page, in that it only lists a maximum of six apps in any category. To see more, you have to click on "View all (category name)"--and rather than expanding the list, that takes you to a new page. Bad design, IMO, and it's going to make it a lot harder to actually discover apps--ironic that you've renamed this page, and at the same time decreased its ability to do what you've renamed it to.