I wouldn't classify the one we (as physics graduate students at the University of Colorado) had as a "lounge" per say. We all had by-ID-card access to one of the top two rooms in "the physics tower" but sometimes research groups would have the room reserved for group meetings, thesis defenses, etc (there was a projection screen for use... if you brought a projector). It was L shaped, so you could still work at the other end... but you'd have to be respectful. Typically groups would put a sign on the door if the room was in use. We did, however, have access at night... when as first year students with lots of coursework, we'd tend to collect. The first year I was there, the furniture was kinda grungy, but the department had it replaced by my second or third year. There was one chalkboard, several large "lunch-style" tables, some chairs to go with the tables, and a lot of those kinds of chairs that can be pushed together to make couches (good if you're working long hours and need a nap). Some research groups (for example condensed matter) had their own lounges (with lunch tables and fridges).
As an undergrad, we had a pretty grungy lounge in the basement (at the University of Dayton, OH). We made it a bit better by repainting the walls (with physics equations and quotes... using SPS funds to buy the paint); I recovered one of the two decrepit couches, and we threw out the other because one of the majors had his mom donate an old couch. Besides the couches there were at least five-6 desks (a nice number for a department that graduated only about 3 majors per year). One desk had a key that got passed down from graduating senior to rising senior... with the most dedicated rising senior getting the key at the end of the year right before the last person with the desk graduated. The fridge eventually stopped working... I think the department replaced it. But that room unfortunately got torn down when the physics building was joined to the chemistry building. I went to visit during construction... and my painting of Schrödinger's cat had it's "alive" head cut off! Guess that measurement was made. We also had an old "tube" radio and record player unit... it worked when we fixed it up, but I think it got thrown out in the construction. not sure what the students there have now.