I bought this a week ago and spent all day on Saturday playing with it. It makes tubes 44 stitches in circumference or straight pieces up to 44 stitches wide and takes up to a sort of medium chunky weight of yarn - just right for a tubular scarf but a bit narrow to make hats.
Turning the handle is a bit boring but it takes the slog out of simple stuff like this. The simplicity really shows off beautiful yarns, though.
But enough of the conventional knitting. What it's really for is making the main bodies of giant knitted and crocheted sea slugs!