I've been back to Memorial Union a few times since the upgrades, and wow, it's gotten even better. They did a great job redoing the space, with nice spaces to study, and better food options.
Grab some food at Piadina Italian kitchen or Babcock ice cream and hang inside at the nice new space that overlooks the Terrace and the Lake. Hang out in the Rathskellar or of course, outside on the Terrace- the most beautiful place on Earth in the summer.