Like hairlessbill, I use the same brake in the front with Ultegra, but I got rid of the travel agent. It's just not needed. Yes, it feels mushy when your stopped, but when riding they don't and you get superior braking and good modulation. You do need a straight wheel and the pads set close to the rim, but once it's set-up, it's as trouble free as any v.
I also use a canti in the rear, but I don't do loaded touring. It works ok, but they just don't brake as well as V's, but it's adequate for the rear in my case. I've had a V on the rear and it works fine (with Ultegra), but you definitely need a travel agent otherwise you get too much breaking; to hard to modulate the breaking force. I went to a canti only as an experiment as I don't care for messing with a travel agent although once set up they work fine.