As an alum for both schools, it's a dream come true. Folks covered the reasons above, but I think we are stronger together. If we can both somehow get football going consistently and pack some stadiums, it will make both schools look like an attractive MWC option.
Sports writers already talk about how the Battle for I-10 is one of the best rivalries you never knew about, and perhaps now that the games will have more meaning, it'll give us a better national spotlight.
Imagine late November in football, or late February in hoops. Both teams vying for a bowl spot or top seeding in the conference tournament. Those games are really going to mean something.