Being SMP in the Guard gives you some extra cash, but you still have attend monthly drills AND you are subject to your unit being activated. If you take the $, you take the risk, so weigh that option carefully.
With the Obama driven military drawdown, which appears to hit the Army end strength pretty hard, the numbers of Army ROTC scholarships will probably decrease, making them harder to get. Probably same for other branches, too. Sul Ross Corps of Cadet scholarships, however are still plentiful, and relatively easy to obtain if you submit in time.
Join up, if you make it thru you will forever cherish the experience. If you pass on it you will someday regret it and wish you had, especially if service in the military as an officer is something you are seriously considering. The best ROTC experience/preparation in America is Texas A&M. Always has been, always will be.