Texas A&M president Bowen Loftin and athletic director Bill Byrne, along with SEC commissioner Mike Slive and Bernie Machen held a press conference Tuesday to officially induct the Aggies into the SEC. You can read their remarks here, and here's the tl;dr version:
The SEC was happy at 12 teams and is now happy at 13 teams. Oklahoma staying in the Big 12 appeared to be a sign that nobody was going to sue over A&M leaving. Working on schedule options. Something about academics. The SEC's TV contract provides for "look-in" negotiations.
Texas A&M feels its football is ready to compete. Also, other sports. The Aggies are open to keep playing Arkansas in Dallas and still want to play Texas. Not yet sure what the Big 12 buyout will be. A&M talked with Slive before Nebraska and Colorado left the Big 12. The SEC has revenue sharing, which the Big 12 didn't have. Kyle Field may be renovated in 2013.
Don't be floored if, within a year, happy to be at 14 teams.