I bought a used Shapeoko XXL a little over a year ago. I love it. I have upgraded the Z axis to the HDZ (Ball Screw) and added the touch probe and the bit setter.It's a very lightweight hobby machine. Be aware that as the size increases, the rigidity will decrease rapidly. Meaning the smallest version will be much better than the largest version.
With CNC machines, you get what you pay for. If you buy the cheapest machine you can find, you'll likely be getting the lowest quality machine.