Hey Poppa,
the QCW Frame, when it came out, provided what the Onefinity machine was lacking to be a complete machine: A machine base. But
- it is rather expensive
- It is by far not as stiff as a welded steel base (okay, no one would expect that). It was even reported that it bent when drilling/sinking on a workpiece
- There is a rather large wasteboard area that you can’t use at the rear (you could even leave that area out when putting MDF slats on it), and a wasteboard room at the front that is clearly missing, as the milling motor is not located over the area with the T-tracks.
The advantage is that the Any Surface Leveling Feet are now included (before, you had to order them separately here) so you can put the machine somewhere and make it coplanar immediately (use fishing line method) and start to mill something.
As for rectangularity (“squareness”) of QCW Frame, I haven’t checked yet. Will report as soon as possible.
On the other hand, I think if you make a 2-3" thick (anti-)torsion box out of 12 mm birch plywood, as many did here, as a machine base / table top, it would not make much sense to use the QCW frame, and such an (anti-)torsion box can be very, very stiff. However adjusting coplanarity would have to be done with shims under the feet then.
I bought a QCW frame to analyze it (ouch to my wallet), and will use it for testing purposes and will report then. But I will not use QCW frame in my final assembly. However many people are very satisfied with it.