The biggest thing I have had issues with are the live tool drive. It is a shaft that runs through the center of the turret, parallel with Z axis. When it get to the turret there is a 90 deg knuckle that drives the live tool. Not that complicated, but have had to rebuild that 90 deg knuckle. We have bought 2 SQT's that needed that done when we bought them. The bearings are not that much, but a bit of work to get to them. Live tools are not powerful, but do fine in aluminum. Not as good as the integrex live tools, but not as fragile as the B axis head. Only 5,000 RPM on live tools, so kind of slow for small tools, but useful.
Live tools can be rebuilt with new bearings and are not a bad job. I run cutting oil in all ours and believe the live tools last a lot longer because of it. Downside is the oil smokes if hogging.
The live tool drive is air actuated, and can get gummy with poor compressed air quality. I would run the live tool drive at least once a week to try to keep it free.
12 tools can be limiting on some jobs. I have ran a boring bar upside down and bored in X- and then used it to rough the O.D. also. I have a stick tool holder that has a pocket for the main, and one for the sub. I took a left hand tool and a right hand tool and milled them down to .500. Then stacked them and run the one at Y1.0, this puts my rough and finish tool in 1 pocket. Have that set up for the main and sub, so I get 4 tools from 1 turret location.