I saw Alice Cooper at The Wolf's Den at Mohegan Sun back in '98. We couldn't get into the smaller actual Den, but we stood on the outside between the slots, and you could still see and hear great. Saw UFO there as well a few years ago as well.
I saw Asia that way as well.
To be clear, Orbert is sort of right. Sort of. Foxwoods has two world class theaters (one about 1,500 and one about 4,000 seats). It's beautiful. Mohegan has the Wolf's Den (300 seats, always free, first come first served) and the arena (10,000 more or less).
The larger Foxwoods theater is awesome; never saw a show at the smaller one. Wolf's Den is what it is, if you can get a seat, and the arena is okay, but it's an arena (and they will cut it down in size if the act warrants it; Extreme played there on the Pronograffiti 25 tour, and I'd guess the capacity was 6,000?). So watching the show isn't like being in a mall, but everything else is. I don't know; it's just personal preference for me, but I like going to Irving Plaza in NY, and walking the streets of NY to get to McSorley's before or meeting up with some of you guys in a local brewery... Plus, for some reason - and I went to college with the CEO of Mohegan (and golfed with him two weeks ago) - it's incredibly hard to get decent tickets at Mohegan. I know a little about how it works, and they, frankly, don't care, because invariably the places are full; they want a BODY there, not necessarily MY body, if that makes sense. I kind of am brewing a bit of a bug up my ass about the artists that play there, but that's for another thread.