It's been a while (too long) since I was an active IDPA shooter, but when I was, I was very active. IMO everyone who carries a gun should at least shoot a couple of matches, even if you're not interested in competing.
Part of my safety briefing to newcomers was this: play this game 5 separate times, and I guarantee it will change the way you carry a gun, the way you think about carrying a gun, and probably the equipment and methods you use to carry.
In short, you learn what works and what doesn't. Reloading on the clock is stressful at first, and manipulating your firearm under pressure is a brand new experience. There is simply no better way to learn these techniques than in a competitive environment. The timer tells truths that you simply can't sort out on your own. Advice and examples from others can help show you new ways to do things, and can show you what doesn't work (everyone has some of both, BTW).
The downloaded magazines is a hassle, but the real reason it's done isn't so much to encourage reloads, it's because the game is played in states where 10-round magazine restrictions are an issue -- thus the game can be played anywhere with no regional changes.
Certain concessions to safety preclude the use of certain real-world carry methods (ankle, appendix, cross-draw, etc.) It goes with my diatribe about "Ways to carry a gun vs. ways to use a gun" and "guns to carry vs. guns to shoot."
The penalty for dropping an empty magazine with a round in the chamber is stupid. I can get on a soapbox all night about this one, because it leads to an inconsistent condition under the rules (The gun in the same condition is "loaded" for one rule, and "unloaded" for others). Long story, better suited for an SO rant at the pizza joint after the match LOL.
I agree that the walk through is in contrast with real world, but given all the things that could happen, the walk through serves to give the shooter a heads-up to potential safety issues, muzzle-safe zones, and an idea of what might be coming at them (remember moving targets are a real possibility). Blind stages, while potentially a lot of fun for experienced shooters, are potentially dangerous for less experienced shooters.
It's the best experience and opportunity to test your holster, handgun, carry methods and manipulation skills you'll ever get for the price of admission. Just remember that a shooting match isn't a gunfight, but a gunfight is a shooting match. By that I mean it's one more tool in the toolbox, but it's not a complete picture of defensive handgun work and skills.
As far as the shooters at Thunder, some of the best IDPA competitors in the country shoot there frequently. There are several championship level shooters there, and if you look real close, you're likely to run into some of Comp-Tac and Smith & Wesson's sponsored shooters there. And these world-class shooters are just as helpful and friendly as the average shooter. I've learned a lot from them over the years.
