A rather touchy issue, and one that is full of potential for problems. Some trainers/schools have very loyal followings but are frowned upon by others. Sort of depends on what you are interested in. One of the more popular instructors out there gets a lot of people coming to his courses, but is roundly condemned by most quality instructors. He tends to appeal to a lot of Rambo-wannabees ("Come take the newest Anti-Terrorist Personal Interdiction Program and learn to single-handedly defeat 10 machinegun-armed tangoes with just your handy dandy super ninja tactical kniife/blowgun/sniper rifle combo!") and those that don't know much better, but those wannabees will rant and rave about how good an instructor he is. And sometimes when dealing with larger sites the issue becomes one of luck, as in which instructor is on call this course? My personal suggestion is to avoid the obvious flakes, such as those you described, but also be aware that some of the reputable schools aren't always that reputable.