Boss products have proven solid & dependable in my experience.  This tuner is no different.  Extremely accurate and versatile as both a tuner and metronome.  Works for bass & guitar whether plugged in or not (most accurate with the cable run).  Purchased it for my son to use with his bass and he loves it.  It has both a visual signal and/or audible chirp when your instrument is in tune which is really nice.  I would have given it 5 stars except for the fact that the battery compartment cover has a tendency to fall off with even nominal impact.  This is easily countered by taping the cover on at each battery change, but I think that looks cheap and a functioning battery cover is essential to the fit and finish of a quality product from a company such as boss and should be a given.  Battery life is fine and the product is feature laden with an easy to read display.  Shame on boss for the loose battery cover, kudos on everything else.