I've actually had the good fortune to attend a game at EVERY Big XII stadium, except for Texas A&M, that is coming later this month ...
Here's how I'd rank them:
Texas - huge, impressive ... great tailgating atmosphere around it, close to Interstate
Nebraska - the pressbox is like twenty stories high! Only place I've been where I felt claustrophobic outside ... there was like a human traffic jam trying to get out!
Oklahoma - the red brick of the structure and the surrounding the buildings is very picturesque
Colorado - GREAT setting, with the mountains as a backdrop, they have this weird indoor track/fieldhouse thing right next door.
Missouri - Big, good setting, lots of tailgating areas around. Decent ...
Kansas - The current renovations have been great ... needs another tier on the bowl side at some point. The concession section near the students still looks like a dump. Tailgating in spread out, no central location ...
Texas Tech - I was surprised by how small this place was ... they have weird false fronts on it, you can't tell it's a stadium from one side ... nice walkway outside with SWC history though
Kansas State - negative points for having the open end on the north side, so all the cold air blows in ... didn't you all do well enough with Snyder there to finally close it up? Lots of good places to tailgate between the football and basketball stadiums.
Oklahoma State - my memories are from the mid-nineties, I know Boone Pickens has given a lot of money for some big changes there ...
Baylor - not very memorable, their student body storms the field before the game instead of after ... strange!
Iowa State - awful, Jack Trice is open at both ends, I've been told by my Cyclone friends this is do it doesn't blow over
Texas A&M - incomplete until October 2007