The Ardupilot is not even close to being as plug and play as a Naza controller. While it will usually fly with out of the box settings seldom will they be exactly the right settings for the frame that you're installing it on. Of all the Atmega/Arduino/Multiwii controllers out there, the Ardu is probably the most complex to get dialed in as there are far more parameters that can be changed and often very small changes can make a BIG difference in how the multi flys.
Once you do get it dialed in it's one of, if not the best controllers of that type. I have one that I'm currently working on getting setup on a test frame as well as a couple Multiwii Mega boards all with GPS. The Megas are the closest to being dialed in and while they compare well to the Naza in calm air or light wind, the Naza handles windy condtions much better overall and the Naza GPS performance can't be matched by anything but a couple other flight controllers currently on the market, one of them being the DJI Wookong-M.
That said, if you're up to the challenge of getting the Ardu setup and dialed in you'll find it to be a great controller for not a lot of $$$. It will work on a 330x, just don't expect it to perform as well as a Naza on an F330 and you won't be disappointed. I would highly recommend trashing the Gaui 10A ESCs and putting something better on there, I have an original 330X that is still flight worthy and the Gaui ESCs were one of the first things that got replaced in order to get it to fly moderately well.
Ken
