1) College football fans - We get to see more games between good teams. Also, there will be several bad "P5" teams left tossing in the wind as a result. (See 1) below)
2) SEC - Adds two historically strong teams to the conference.
3) ACC and B1G (maybe) - If they play their cards right, they could cherry pick Big12 leftovers (eg. Kansas and Iowa State to the B1G and West Virginia to the ACC).
4) Crappy SEC teams - Arkansas, Mississippi State, South Carolina, and Vanderbilt all see their "value" rise by being the red-headed step child who got invited to the big boy's table at the right time.

Biggest losers in OU/UT to SEC?
1) ANY Big12 team not fortunate enough to be invited to the ACC or B1G - These will be "lucky" to be picked up by the AAC or MWC and will, therefore, be relegated to G5 status.
2) PAC12 - The PAC12 is already on a media/streaming island. As the Big12 has only two teams that bring any "big time" value to the conference (OU/UT), there are only three teams that bring equivalent (or close to it) value to the PAC12...Oregon, USC, and Washington. Adding any Big12 leftovers not taken by the ACC/B1G further diminishes the value of the PAC12.