The 101 is a dub bassists dream. Treated as an EQ pedal alone it allows you to get the huge thick dub tone without pushing your amp EQ to its limits. I use the 101 constantly in my music. When the pedal is bypassed the drive knob still effects your sound, so it effectively becomes part of your pre-amp anyway and adds a little analog goodness to it.
Many tracks I use it on with an Octave pedal to fatten up sub. It has a whole host of functions without an expression pedal.
Add the expression to start using the synth swells like you asked about in the 1st track, or in fact that you hear in millions of tracks, allowing you to push the sound from deep smooth sub, to high fizz and back (stopping anywhere along route).
I got mine on eBay for £105 plus shipping, plus £20 on an EP-2 expression pedal. For what it can do though, I'd be happy to pay the retail price if mine packed in!