This pedal is the collaboration of Ryan from Fuzzrocious and MXR to create an amazing Rat clone specifically for bass players. I'd say they did a dang fine job it, the pedal is exactly what they say it is. There's a certain character to it that gives it the Rat vibe that many guys are looking for. Of course you will always have naysayers, but I say this does a pretty good job.
My biggest complaint, and this is common with distortion pedals for bass, is how they reactive with higher output basses. I use the term "active basses" as they are typically much higher output than regular passive basses. I tested this with passive basses first, two stock Squier bass (CV P and VM J) and my Ibanez SRX3EX w/ a 3-band Bartolini preamp in passive mode. Using these basses, it sounds fantastic. It's very full, the distortion range is great, and it adds some gnarly hair onto your tone.
Switching my Ibanez to active mode just ruins the whole thing. I adjust the volume and distortion on the pedal to no avail, it just can't handle that much input signal. This is a "problem" (at least in my opinion) with other pedals as well. The EHX Bass Big Muff Deluxe resolved this problem beautifully by simply adding a -10db switch onto the pedal. No matter what bass I use with it, it sounds great. The Blower Box and MXR M85 are pedals I'd LOVE to use with my active basses, but I'm restricted to only passive due to their lack of an input pad. I don't want to affect the tone of the instrument by rolling down the volume, not to mention keeping my place should it get moved would be a serious pain. I'd deal with a larger size box just to have this option.
My only other gripe is that the 9v adapter plugs into a hole right underneath the 1/4" input. This is a pain and I often wonder why they don't just put it on the top like so many other pedal manufacturers. It gets in the way of my patch cables and just seems stupid.
If you play passive basses and aren't bothered by the adapter port, this is most assuredly a great pedal to have. Make sure you like the Rat tone or try one out before buying. It's not for everyone, but for those who do like it, this is a Godsend.
MXR M85 Bass Distortion
The MXR Bass Distortion dishes out big gnarly tones with all the low end your bottom-dwelling heart desires. Working closely with indie pedal phenom,