I flew 10 packs yesterday trying to test baro only alt hold and loiter with the sonar disabled. I also wanted to test my Mavlink to Remzibi converter for my onboard video out. I spent quite a bit of time getting comfortable with "simple" mode - especially flying high and farther away were orientation becomes a factor. Simple mode is awesome and worked well for me.
Here is a link to some video where I really pushed the stick hard in simple and sort of half flipped it.
I was using a larger pack on the stock frame (3300 mah) and I think that I maxed out the ESC/motors - as watching the current draw from the OSD. It was zipping along, I rotated yaw so the camera was pointing north, and then it started pitching up vertically - quite startling, but releasing the stick recovered nicely. I have a small plywood platform for the tilt/pan camera and that may have contributed also.
Baro only alt hold sort of worked, but the quad eventually slowly dropped to the ground. The dropping out of the sky was very consistent and I have logs for all of the flights.
Loiter was very problematic the quad held position for 10 seconds or so and then started to dart off with max tilt in the southeast direction. I'll check the logs out today.
I'll also load 2.31 and re-enable the sonar to see if there is improvement for me.