I have the sh-cnc 6090 (600mm x 900mm). For the size and price, you can not beat it.
The only problem I have had was to replace x and y ball screws. The factory forgot to put grease fittings in the ball nuts. Needless to say after a few hours of operation, the ball bearings wore out. There was absolutely no problems with getting replacements. So, when your machine arrives, check the ball nuts for fittings and give it an extra shot of grease to be safe.
Overall I am very satisfied with the machine.