2years ago I worked at a job that needed me to configure different quadcopters on different autopilots. I have done ap and micropilot etc.  After quitting the job for various reasons I bought a 3Drobotics quad kit with ardupilot. 

Now since I have many projects that actually need to be dropped from heights (starting from sensors and ending in skydivers practice tools) I decided to upgrade my aerial system to this: The gopro is just for size comparison

PX4 works like a charm. The first time I fastened the props I had a perfect flight. This was not like the arducopter. I got all the logs I needed to evaluate the system in one go, there is magical and fast connection to usb and all those little things. 

Just calibrated it, configured the board and compass orientation and threr PID-s a little lower (since it has 330KV motors).

I am flying with 6C and 20Ah batteries so that meant I had to mod the 3D robotics regulator for this (pulled the original regulator module out and added my own 30V reg). Also switched the voltage divider resistor to something that fits my configuration better. 

This thing just flew without any pre-tuning on ropes or at hand (thou to be honest, getting props to spin up while not 3m away from the device is not an option with something like this). 

Soon I will go for autonomous system configuration, but today is not that day, and I have done that so many times that I do not expect to see anything new happening there. 

Also, just for the record the current test configuration gave me worst case flight time of 32 min and best case of 40 minutes. This is without any payload and with little calculation magic to get the numbers. I just could not wait to get to the logs so real time was around 10 minutes.  

Also for those who wonder, the frame design is custom and not the cheapest one. but yes Pixhawk is awesome. 

Do Recommend. 

Some extra pictures: