I get the vibe from Husker fans that miss the Big 12 their reasons behind that mindset is that they miss the "sure" wins that came when competing for the Big 12 North title. They miss the easy wins that SHOULD occur against teams like Iowa State, Colorado, Kansas and Kansas State, and only having a must win game against Missouri to really lock ourselves in as the North contender for the title game.
The Big 12 misses Nebraska because when they left, they took the last conference championship game with them.