The student union is a great hub. It has a lot to offer for students and anyone who is visiting on campus. There are lots of food choices (Taco Bell, greens to go, Panda Express, that sushi place, metro pizza) along with the POD that is your on-campus convenience store. There's Jamba Juice, so you get your delicious fruity needs, and now a frozen yogurt place.
With a computer lab upstairs and lots of chairs/sofas everywhere, the SU offers itself as a place you can study at. The second floor has a more quiet atmosphere whereas downstairs is quite busy and active.
Downside... I wish this place had more breakfast options.
Protip: add money to your rebel ID for a slightly cheaper purchase. Using your rebel ID means no taxation on your bill :)