Good enough for what? I'd love to have a lawn mower which can dump grass clippings in my compost pile (mulching them and leaving them behind is better for the lawn, I know, but my wife is allergic to grass so this would basically mean she never gets to use the lawn). Also, we have two apple trees which spend a few months dropping apples on the lawn, so I'd like to have a robot lawn mower which can pick up the apples and toss them in the compost pile too. Oh, and there's a gate separating the front yard from the back yard, so it would be great if it can open and close the gate.

Robot lawn mowers are getting better, but I have yet to see one which can handle every situation that humans routinely handle.