I got my instrument rating in a little over 13 days through ATP. How fast you train has nothing do with how confident you will be IMHO. My instructor and I were out flying in the soup every chance we got. I picked everything up fast, if you told me holding one time I was mastering holds every time there after. Accelerated courses are great for the right people. Trust me if I had to it all over again I wouldn't of done it that fast. 3-4 sims a day with several flights was stressful but I didn't feel any less confident than if I had taken 3 months to do it. There's lots of schools that I've seen that won't even let you fly IFR when training. One thing I will give ATP as they not only encourage it but recommend it during training. The only time you can't is on XC's the airport has to be VFR. Other than that you can fly in it all day long as long as it can be done safely.