Due to a chronic injury, I have not been able shoot the IDPA as much as I used to. About 11-years ago I even wrote and thaught, in a semi-annual basis, and Introduction to the IDPA class which was well received by both novice and experienced shooters and competitors. The primary purpose of the course was to educate anyone who was interested in participating in the IDPA about the scoring, the equipment rules, and other nuiances about this sport.
The last time I shot anything USPSA related was a 3-gun match about 9-years ago. IMHO, the USPSA is counter to survival since the non-use of cover is actually advantageous to a shooter. Plus the equipment you must have to be competitive is not the type you can use on the street or on duty nor do they require the use of cover (who in their right mind would carry a tricked-out 1911 with a compensator, a half dozen magazines, topped off with a red dto scope and carried in a skeleton holster?).
If you expect to receive any kind of "training" while competing in the IDPA (or USPSA, for that matter) you will probably be disappointed. These are shooting games, not real life. As I tell my students, if you want realism go to downtown DC or someplace like that and start something with the local gang-bangers.
The best you can get out of either IDPA or USPSA is practice under pressure. I have seen Combat Veterans with multiple tours and firefights under their belts and Police Officers who have been in numerous gunfights succumb to the sound of the shot timer's buzzer. It's amazing how much artificial stress can mess up a person's peformance.
Whether or not you shoot IDPA or something else, it is important to approach it in the proper manner. It's probably the best practice and one of the best venues for testing one's skill and equipment. JM2CW.