I don't remember the exact numbers, but most road brake levers pull around 11mm of cable, while mountain bike levers pull about 23mm of cable. The geometry of the powerful linear pull brakes requires more cable--thus the 23mm pull on the mountain bike cable, it creates more of a mechanical advantage at the brake pads. The shorter arms on the Tektro Mini-Vs requires less cable pull to move the pads given amount--and thus has a bit less mechanical advantage compared to a standard linear pull. However it's a compromise. They do need more cable pull than a road sidepull or a properly setup older style cantilever.
They are great brakes, but the setup is critical to use them effectively with road levers, and they require more of the pull of the lever than sidepull or old style cantis, so they have to be adjusted just right. However, in my experience, their braking power is superior to the older style of road brakes--that's why Burly puts them on the tandems. I use them on a touring bike that almost always has a trailer with a load in tow. I didn't want to use a travel agents or other cable amplifying device because I wanted to keep my braking system simple. The Mini-V's have been a great solution for me.