I know I posted this thread quite some time ago, but I decided to grab the TC Spark Mini yesterday. Unplugged my Boss ODB-3 and threw the Spark Mini at the end of the signal chain. Turned the pedal to 12 O'Clock and the sounds that came out of my amp!!!!
The sound is so full and rich, and I can set it to just saturate my preamp, or hit full on grit.
The pedal looks so cool too! I want to replace all of my boss pedals with fancy ones now :P
edit: This pedal also adds a bit of brightness past 12 O'Clock, but it isn't out of place and the bass isn't really affected