We went to a Denver game last year. I've been to a few stadiums (Ralph Wilson, Jaguars, Cowboys), and the transportation to and from Sports Authority field is outstanding.
We stayed at a hotel in Cherry Creek. Union station was not too far from the hotel. A quick drive to Union Station, park the car and jump on the train to the stadium. It's a short walk to the stadium from the train drop off.
After the game it looked like it was going to be hell to catch a train back, but I was quite impressed with the organization of the lines and the extra trains to empty the place.
I'm looking forward to the Dec 7 game. We paid $350 per ticket for section 308 last year, not sure what it will cost this year. But it's a lot cheaper to drive up to Denver from Amarillo (5 to 6 hour drive) than it is to fly to Buffalo. On the flip side $350 per ticket bought us indoor tickets at the Ralph for the Thursday night game against Miami a few years ago. Ticket price wise, the Ralph is a bargain.
Go Bills.