Solid build, plenty of extra parts for really any use-case. Currently used for racing/driving and flight sim. There are also plenty of other devices with 4040 based build which bolt right onto the unit. Very easy to put together (instructions are minimal but pictures were sufficient and knowing what parts are load-bearing make most connections obvious). I added the caster wheel base to my order as well; very solid connection from the casters to base of frame, used to move over carpeted surface without any issue. Casters have a nice wheel-lock in place to prevent movement. Selection of 4040 extrusions has a more solid center section than other pieces you may order from a different distributor; see center wall thickness compared to other extrusions you may receive from other suppliers. Overall very, very happy with build. Next step is to add a DOF motion system that can support weight of the rig. Would purchase again if I needed a second rig, would definitely recommend to anyone looking for a sim rig.
Other additions: Sparco racing seat, slider rails for seat base and pedal base, Fanatec DD2 base, Fanatec H-Shifter, Fanatec handbrake, Fanatec inverted pedals... note, I bought these a long time ago so I just moved them over from my old rig (otherwise I would have probably mixed and matched a different setup), Fanatec e-stop, keyboard tray, monitor mount, and overhead angled monitor mount, siig powered 20-usb hub, 3d-printed handbrake and h-shifter mount, 3d-printed mount for Varjo XR4, dual 1/4" camera mounts for steam lighthouse, 4-point harness seat belt. Depending on how lazy I get I'll probably get another rig just for flight sims so I don't have to keep on swapping out the pedals...
I'm not any good at racing or flying but the experience of losing in VR is still amazing :D