I am a Navy Reserve officer who has served 5 years active duty and 20 years in the Navy Reserve.
During that time, I have seen many individuals who get in, stay for a while, and then depart in manner that has many similarities to what our President experienced while he was in the Texas Air National Guard (TANG).

1. Getting In. There is no numbered queue. A person with outstanding qualifications can have his record pushed ahead of others. (Clinton's very strong "presentation" to Col. Holmes got him a spot in a ROTC program at Univ. of Arkansas, a spot that got his draft notice canceled, and a spot (and commitment) that Clinton then reneged on.) Selections and preferences can happen just like a private sector company hiring the last guy who comes in the door over 50 candidates who showed up earlier.
I have conducted interviews of people seeking to get a Direct Commission in the Navy Reserve. They need a college degree - and after that, based on the interview, intangibles such as enthusiasm, one record might be pushed harder and faster than many other records. To suggest that the TANG selected GW Bush "out of order" is to be ignorant of how the military (Active/Reserve and Guard) really works.

2. Service. Even the liberal media concede that GW Bush's record of flying the F-102 was exemplary. There are evaluations that are public record attesting to GW Bush's skill as a pilot.

Getting out (sometimes - pushed out!)
3. WHAT IS MISSING - Sometimes the Services Let People Go - or Even Push them Out:
The discussions miss something very key. After GW Bush qualified as a pilot, the Air Force and Air Guard made a decision to retire the F-102 airplane. When this happened, GW Bush became one of many pilots whose presence was no longer "essential".
THIS IS KEY: The Navy and Air Force have many times "RIF'ed" (Reduction in Force) - i.e. "laid off" pilots who no longer had a plane to fly! The services might select some pilots to go through retraining to qualify on a different plane; those pilots must accept the additional committed time to serve if they want the retraining. And if the service has sufficient inventory of pilots, then the pilots who flew retired planes might be forced to go elsewhere - perhaps go serve on surface ships, take some desk job, etc. Many times, the services have separated the pilots from service, discharging them into the civilian world.
In 1978 - the Air Force did a RIF, and hundreds of pilots who were in basic flight trainining or had just completed basic flight school were discharged from the service. The Navy and Air Force RIF'd pilots (and many other officers) in the 1993 - 1994 initial "gutting of the military" when Clinton took office. As the services have retired planes - pilots become surplus (and many times, are let go, or even forced out!)

EVEN NOW - force "shaping" can take place. The Navy just RIF'd 1000 junior officers. (This - in spite of the fact that the military is mobilizing and sending reserves and guard over to Iraq!!) These cuts are aligning the Navy Officer Corp. with the smaller but higher tech force that is being developed. The Navy is changing from destroyers and cruisers that used to have a crew of nearly 500 persons to 350 persons (present) toward 95 (the goal in about 5 - 10 years). Privitization is shifting shore-based jobs that might have been done by the military - to civilian/contractor jobs. The goal is to trim personnel costs and buy more hardware - more ships and planes.

SO **********
When the F-102 was retired, GW Bush became "excess". He wouldn't be sent to fly another plane without retraining. He would not be qualified to do many jobs without additional training . . . so he would be allowed to do "make work" jobs - such as training and administration of reserves, writing up reports, etc. He would have no critical skills, and there would be no critical tasks where his presence would be essential. The Reserves/Guard would be very flexible in rescheduling of drills with someone like this. (I have seen Direct Commissioned Reserve Officers STOP drilling after 3 - 4 years because their work/family schedules conflicted, and they were not doing anything critical . . . and the Navy Reserve did not have any critical need for them). (I have also, as CO of reserve units, allowed flexible drilling to help reduce potential work or family conflicts, and usually this allows me to get efficient work - especially if they do a block of work, such as when GW Bush did 36 days straight.)