Maybe I'm just being unusually dense for the moment, but how does this help the user make a better decision about what plugin to install?

Is there additional information being provided in the modal that isn't being provided in the repository listings? If not, how can this possibly make searching through the 30,000 plugins easier or more informative if the search is combing through the same information at the repository website? If so, why does the modal have better search features and results than the repository?

It's pretty, but it's also something I'll never use, mainly because I still don't trust the WP.org installers. It took years for me to finally trust doing updates from the Plugins menu, but for first time installs, I'll still go FTP for that. Only way to be sure :)