I use the Little Big Muff Pi for 2 reasons mainly, first one being, I needed a warm fuzz sound for recording riffs and the second reason being sustain for lead playing since my pickup output is somewhat weak on the e and b strings. It does both of these jobs for me very well.
Some other things i noticed: The casing is very sturdy, the controls are very intuitive and can blend some crazy sounds, depending on what you dial in the pedal can create crazy loud feedback but just keeping it away from the amp fixies that issue.