I do know it is very competitive. DS who will be a firstie as of this Wed after graduation of the Class of 2017, has a friend looking into it. This friend has already gone through a few steps heading into his senior year..I'll see if I can find out more.
There are plenty of good articles. Just google search.
Here's a breakdown of the 3 main officer jobs:
STO are Special Tactics Officers. These are the guys that are leading Special Tactics Squadrons. That's AFSOC.
CRO is Combat Rescue Officer. These are the guys leading the Air Force CSAR missions. This is PJs and SERE. From what I understand, there are some CROs in AFSOC.
ALO is Air Liaison Officer. These are the guys that are running Air Support Operations Squadrons. An ASOS is an Air Force squadron on an Army post that's responsible for coordinating air power for the Army. Traditionally, this was a duty for rated officers, however now it's an actual career field with its own AFSC that you can commission right into. You'll work alongside TACP. TACP can go AFSOC (I believe they go to the ASOS assigned to the 75th Ranger Regiment).
The main differences here is: STO's are ONLY SPECIAL OPS. (AFSOC). They go through all the training of all the other jobs. They go to schools with Combat Controllers; TACP; Scuba; Survival; Parachute; etc. They go through all of the same training as all of the enlisted personnel that they will be leading. Being they are only in Special Ops, they can sometimes have PJ's/CRO's, ALO, etc. with them for a special ops mission. A CRO/PJ can be at a normal base doing normal search and/or rescue missions. ALO are the same. They can be involved in normal military work coordinating air power for the army. Basically; normal military engagements. But for the majority of training, most of the STO, CRO, ALO, and enlisted controllers, PJ's, etc. go through many of the same training. It's their advanced training that is different depending on the job.
STO on the other hand, is ONLY assigned to Special Operations. They only do Special Ops missions. Usually a much smaller group. Last time I asked my son, I believe there were about 85-90 STO's in the entire air force. They work closely with the other service's special ops teams.
Obviously, each mission is different. For STO's, some missions require officers on the ground with the team in direct action. Sometimes, the STO is doing more of the planning. A CRO I don't believe ever does an actual rescue. Not that they don't know how to. You need to know how to do that for which you are leading others to do. I just don't believe they actually jump and rescue, or learn all the medical training of a PJ. The STO will work with CCT (Combat Controllers - enlisted) on the team; possibly embedded with other military branches; possibly some TACP/ALO; etc. But again, for the STO, they are only doing special ops.
As red dragon mentioned, it is very competitive. You have to APPLY for it. IF AFSOC reviews your application and they want to give you a "TRY OUT" (Called Selection), you will be invited to go to Hurlbert Field Florida. When my son went, he was currently in Grad School. He went down to florida. 26 or so started; 12 made it through the week without quitting; and of the 12, only 5 were selected. My son WAS NOT one of the 5. But fortunately for him, during the outbrief, the Colonel thought he had potential and offered him another try 6 months later. Again; they started with about 25; about 11-12 made it through without quitting; and they selected about 5. He made it the 2nd time.
But that's not the end of the competitiveness. Once you get in, you have about a year of heavy duty training. Combat training, air traffic control, parachuting, Combat Control, etc. If you fail any of these, you're generally gone. Sometimes they will put you back in training and let you try again. After the first year is done, and assuming you make it through the Combat Control School (Which you're there with enlisted too). You'll finally be an official STO; get your beret; etc. But now, there's about another year of advanced training. Advanced scuba; HALO (Free fall high altitude low opening parachuting); and quite a few other classes. Total training time is 2-2.5 years. Assuming you don't get slowed down. My son had to drop back a class for a couple months because he had to get his appendix taken out. And Navy Dive School requires he not dive for 3 months after the surgery.
Anyway; I know most of my info was about STO. But that's what I'm most familiar with. For officers, it's about as close to getting "Dirty" as you'll get. If you really want the dirt, then enlisted is where it's at. You can be a Combat Controller or a PJ. When I was in the military, I was enlisted. I worked with many of the CCT/PJ and other similar jobs. (They are BAD-A$$). But for being an officer, STO is definitely a noble ambition.