Union Station is the hub of three transit organizations in Toronto: TTC, GO Transit and VIA Rail. Along with being such a nexus comes the understanding that there is a lot of chaos, especially during commuting hours for GO and TTC in particular.
If you are making a connection, there is a fair number of fast food spots in the station. Dairy Queen, McDonald's, Tim Hortons to name a few. I realize that since it's a really high traffic area, there are some challenges with keeping the place clean, but the bathrooms are a bit grotty.
One beef I have with Union is when I catch a VIA train, it usually has unassigned seating. This means people start jockeying for seats 45 minutes before the train is supposed to leave, and a huge line ends up forming. I don't know why there can't just be assigned seating. I'd rather not stand in a line for 45 minutes before my train leaves if I don't have to.