that's how i run my DDSS, at 18 v
all i can say is, i prefer that sound over the 9v.
it is a bit as you describe, the idea that the sound 'opens up' a bit, and is a bit less compressed.
for me, it's a bit more hi fi, and easier to dial in the tone knob.
you can go with less treble and presence, but still have more clarity and grind at the same time.
i have a song recently finished, that features the DDSS at 18 v all over it, it's the best example i have of using this pedal for both rhythm sounds and lead guitar tracks.
all the solos throughout the song feature the ddss.
i'm driving the lead channel of a vintage Mesa Boogie Mark2b with it.....
lead channel is set for a crunch rhythm sound, fairly clean but gritty, then pushed with the DDSS with everything near high noon, maybe down on the tone a bit.
http://soundcloud.com/bats-brew/walked-away
Barber Katrina Relief DDSS, Barber Tone press, Carvin DC200K, Williams Special, USACG strat, '81 Mesa Boogie Mark IIb head, Avatar vintage cab w/Heritage g12h, Yamaha DG Stomp, asstd. other pedals