I just added a Travoy to my arsenal and tried it out for the first time yesterday. Thumbs up. I've gotten so used to only being able to carry small loads that I actually had a hard time filing it when I went shopping for groceries and lots of bottled water. I live in a 2nd floor apartment and it is easy to carry down empty and pull up loaded.
The clamp is also small enough to co-exist with other bag clamping systems, like the Carradice quick release clamp (also on my seatpost).