Ok well I'm going to answer this but I want to make it clear because as most of you know I build machines for people that in no way what I'm about to say is said to pull this machine down for my own purposes because I really don't need to. Neither is it intended to say anything about the guy or company building them as I don't know him at all.

What you need to do is look carefully at the machine and ask some questions about it.!

#1 The frame is a welded construction which at first might seem good, but as any on here who have welded a frame will tell you they always twist and move. Also, it's critical to accuracy that the surfaces the rails fasten onto are exactly on the same horizontal plane and vertical planes. This is why we go to great lengths machining or using methods like epoxy leveling.
This machine as NONE of this done to it. Add to this that the 75mm with 3mm wall thickness isn't that strong and being thin-walled it resonates quite a lot which again affects quality of the cut.

#2 Gantry is a very weak affair that's better suited to a plasma machine, just.!!... and again no signs of any attempt to make sure it's flat and not twisted. Plates and connections to ballscrews and key areas like Z-axis are flimsy thin things.

#3 The motion control side is done from the PC with a £5 breakout board. From what I can see he's using commonly used refurbished Dell PC's, which are actually the same ones I use with Ethernet controllers.
If so then I can tell for sure that the parallel port on these is very flaky and I use exactly the same setup for testing and setting up machines with the same KKo1 board and they crash and lockup for fun. So bad that they won't even pass the Linux CNC latency test for using with a parallel port.

#4 Nema 34 motors are just wrong choice for a machine this size and I'd put a wager on it they are run on low voltage to boot. NEMA 34 motors need lots of voltage to get speed. Thou he does use 16mm pitch screws which will offset this to some degree, but still not a good choice for several reasons.

#5 The rails are the round type and the cheap variety, in fact looking closely at the components like ballscrews and BK/BF bearings I believe they are the lower quality units that come out of China, Not all ballscrews and bearings coming out of China are the same quality. Again many on here who have built and bought from China will confirm this.
I've spent a lot of years using various suppliers in China and I'm pretty sure these are the lowest spec available and is how they can sell these machines at this price. Which is ok but they wear out quickly and get sloppy fast and when fitted to a machine that isn't built very accurate to start with these all compounds to give a not so accurate machine.!

#6 The Z-axis is a weak affair fastened to flimsy plates that extend too far at 170mm with a heavy spindle on the end. The end result will be vibrations at the tool which is exactly where you don't want it.!

Other than these things then it's fine for light hobby use provided you are aware of its shortcoming and low-quality components. Oh and the shitty parallel port which I wouldn't trust to run my kettle.!