Wow, great thread. I've been sitting through FITC (Flight Instructor Training Course) at NASP for the last two days. Reading all the posts in this thread have been far more productive than the 12 hours or so we spent in class over the last couple of days.
Best IP(s)- The ones who let me figure things out on my own, to a certain extent. I had two, specifically, when I had issues with a certain maneuver let me work on it without commenting, then were able to say, "Ok, now that you have the feel for what you want to do, try this." causing the light bulb to go on. They let me get the "feel of the plane" without being any penalty for those rougher moments when you're figuring things out. They realized that sucking happens a lot before you get good
Worst IPs- The bullies. There have been two. Both acted like they were too good to be instructing students and made it well known that they hated being there and took out their frustrations on students. They didn't explain what you may have done wrong, just that you sucked. Gee, thanks, I have less than a 10th of the flight hours you do, I know I suck, tell me something useful. Ultimately, what I took away from them was not to be an asshole.