Yeah. It usefulness can be very area-specific. I used it planning a route out of Rapid City, SD. At one point it chose a road that turned into nothing more that a dirt track with a hump in the middle. Guess it got so bad the Street View car had to turn back.

Another thing it likes to do is route you our of the way in oder to take advantage of bike/recreation trails, even if they are short.

It's a decent starting place, but you really should investigate more deeply, especially out west. Case in point: Out of curiosity I asked for bike directions between two Montana towns on ACA's TransAm route. Google returned a route that used some remote, unpaved roads with no services. Great if you like that sort of thing and have the equipment to handle it. Not so much if you don't.

Another example you can try for yourself. Bike directions from Wise River, MT to Twin Bridges, MT ignores a perfectly good (and pretty) frontage road along I-15 between Divide and Melrose. The road between Melrose and Twin Bridges is 100% unpaved and is very rugged and hilly in places.