1) After all the reading I'd done, I expected it to be "brighter by nature." Set flat, I had to turn up the horn on the Epi 410UL, and LDS 2x8+horn from 9 o'clock to noon to get the same top end results as the M6.
2) The low end is very controlled. While the M6 typically has me dialing it back to control it, with the F1, lows are great flat. Tight, controlled, and substantive...how is that possible from an amp the size of a cigar box?
3) Plays well with others...both basses and cabs, the F1 seems to pretty well get along with everything I threw at it without complaint.
4) EQ...The M6 was my first satisfactory venture into non-semi-para eq in a loooong time. WT800b, TFB550b, Walkabout...see where I'm coming from? The F1's points seem well chosen, and work well.
5) Holy Small Powerhouse Batman! I think Lil Betsy here will cover anything I'll find myself doing. While it misses fitting in the gear pockets of my Lakland or G&L bass-bags by the width of the knobs (bummer!), it fits in the gear pocket of my Pro-tec Contego...so there

6) The VLE and VPF do their jobs well, and fairly subtly. VLE can tame a bright horn/bass while leaving your baseline eq alone, and VPF can subtract a bit of mids, and add a controlled bit of low end plus top end sheen quite nicely.
I tended to like eq flat, perhaps trimming a little off the bass knob while cranking volume; VLE and VPFboth at about 9 o'clock...
It'll be some time till I have a chance to stuff the double bass thru her, but so far, I like it pretty well.