I use one on my 5 string bass and it works really well. It takes a bit longer to register the low B, but some of the other tuners I've tried struggle to even detect the low B (even though they claim to be able to do so).
It's perfect for the four main strings on a bass (EADG) -- but it does NOT register the low-B on my five string. It just doesn't hear it. However, if you stand in front of your amp with volume up, even a little, it'll pick it up accurately. I tune my bottom string down to A, and the tuner picks it up, as long as the amp is on.