very good modern bass overdrive that can go from a little crunch to heavy distortion. main point: it does not kill your low frequencies. lots of options which is good because different bass guitars deliver very different things and i could adjust anything from a p-bass with flatwound strings to a BEAD-tuned modern heavy bass. i particularly like that you can blend distorted and clean signal, extremely useful when playing together with high gain guitars. this is most probably the best overdrive i've come across in more than 20 years of playing electric basses. haven't had it long enough to judge sturdiness, but the quality seems good.
reason i gave it four stars overall is because there is one thing it can not do: despite the name, there is no tube in it, therefore you will not get tube saturation/sound. you can of course add just a little dirt to your tone and most people in the audience will never even think of the difference, but if you are looking for tube sounds, this is not your gadget. buy something with a tube in it, the darkglass has it's strength elsewhere.