We've been happy with Big River and for LATE night it may be the only option. In Dec '98 we arrived at BWV pretty late as DB/SIL's plane was delayed. We were stuck at MCO for 4-5 hours waiting for them, as we were sharing the rental car.
It was after 11 by the time we checked in at BWV and went to eat. I think BR was our only option at that time. DH and I were pretty hungry as we'd been waiting for them before eating. DB/SIL weren't hungry as they'd flown 1st class and had nice meals on both flights, plus due to the mechanical problems they'd had food vouchers in their connecting city - and of course they HAD to use them. Our server was nice enough to suggest a kid's meal for my DB (and he is WELL past childhood) as all he wanted was a hot dog.
Actually, we just ate there again this December with DB and SIL - as they were passing through on their way to the airport returning from a cruise. (We live in different states so we take any chance we get to see each other.) Again we had wonderful service with a delightful CM.
I have no doubt that others have had poor service, but we've been blessed with very good service at Big River. So, don't count it out because others don't care for it, but also I wouldn't get my hopes up for wonderful service just because that is what we've experienced.
IMHO the biggest problem with WDW restaurants is consistancy. This past trip we ate at two restaurants twice because the first time was WONDERFUL. Both times the second visit, a few days later, was so-so - in terms of food and service.