I got given one a couple of christmases ago as a gift.
The smaller 'base' ones are fine on the 25mm round bases.
The larger pieces are too large to fit onto a 40mm base (being a tad larger than the overall diameter of the base - not the flat top where you normally put models, the larger bottom diameter) and require some shaping to get them to fit (or mounting onto a washer or somesuch.
The ballast and gravel are ok, but need to be properly sealed to stay on bases.
The etched brass bits are good, but make sure you use clippers meant for cutting metal (like wirecutters) or you will notch them.
I wouldn't pay full retail for it (but I have access to a model railway supplier, so I know where to get cheaper basing materials from), but for some, it might save them some time.
Hey! Where'd ... Everybody ... go?