Judging from other blogs most people use theirs as a dining room. We on the other hand envisioned it mainly as a home office along with a playroom for the kids and a spot to relax. We originally had a small couch in there but replaced it last year with this chair from IKEA. Our older son's big gift this past Christmas was an Xbox One (and let's be real here, I wanted to play it too) and we didn't want it upstairs in his room. (See previous parenthesis among other reasons.) I had been looking to add a television in there for a while already and I managed to catch this 39" 1080p Insignia Roku set on sale for $199. It's the perfect size for the room and while we don't have a cable outlet in there the built in Roku means our younger son can still watch his shows without tying up the main television in the living room.
There are two regrets I have with this room:
1. We should have added a ceiling fan rough-in. It can get a bit warm out there in the summer even with the blinds and curtains closed. Eventually I'm going to talk to an electrician about the feasibility of installing one but it would have been far easier and I'm betting cheaper too if it had been done during construction.
2. Not as much of a regret as #1 given the amount of natural light from the windows and sliding glass door but do wish we'd gotten the two extra windows. On the other hand having a solid wall gave us a good spot to hang our college diplomas and I'm not sure where we'd put them otherwise.