Seems Pretty Good!
I've never worked with a product like this before so it is a bit tricky to rate. But I assembled it easily, attached it to the platform easily, it seems pretty sturdy, even when loaded with big weights to prevent it skittering across the surface of the grass. Seems to make lots of holes in the grass. So overall it seems pretty good compared to what I'd expect.
Of course I can't tell for a while whether the lawn is any better but I guess it must do it good. And buying this means it will pay for itself in one weekend compared to getting someone in to do it for me.