I have the Milk Box. It's one of the newer ones. I think it's a great way to get into compressors without spending alot of money.
I really only kick mine on if I slap or pop. For that, I've found it works really well in evening things out. For this, I have my settings, from left starting with level to right: 12 o'clock, 10-11 o'clock, 9 o'clock, 9 o'clock. This sounds close to unity and noise is a non-issue at these settings. I usually have it turned off. I'm not sure about the buffer. It sounds fine to me without any loss of highs or lows, but I like the tone of my bass better when it's out of the chain. Not a huge difference, but there is just something not quite as tonally pure with it in. For this reason I am buying a simple true bypass looper. BTW, mine introduced some extra hiss with the hi exp knob turned all the way down. Brought it up a smidge and it went away. Other than that, great pedal!