Well they're on El Capitan now, so as far as I know you can't even get Mavericks anymore.

I'm on El Capitan and it's fine, though I don't know if Pioneer has updated the firmware on their products to be compatible yet (I use Traktor and the Z2/D2s so I don't keep up with their stuff).

I use Ableton, Logic X and Pro Tools 12 - all work fine. Never had any issues with any of the stuff you're concerned about, with the exception of the first couple of months - a bunch of Native Instruments products had an issue with the AU certification, but that's fixed now. Haven't had any more crashes with any product more than previous versions of OS X, and it's never been a major setback.

Well they're on El Capitan now, so as far as I know you can't even get Mavericks anymore.

Previous downloaded OS can be found in the app store under "Purchased."

As for Mavericks, I think it would depend more on what machine you are running. I just did a clean install with El Capitan on my 2011MBP and it works better than ever and Live 9.5 works great. I had issues with my SSD on Yosemite and Mavericks because of the Trim feature, but after upgrade I have a serious increase in speed.

On the other hand, I just reverted my pals 2014 iMac back to Yosemite for stability. His last install was upgraded from Mavericks to Yosemite and then to El Capitan and he was experiencing the same issues that most people were complaining of when using NI plugs and MPC software.

I say go for it. It was one of my more stable installs on a few computers.