I have not used twist type shifters, but I do mechanic work on our school district's bike safety fleet. Out of the 36 bikes, 24 of them have twist shifters. I can attest to their durability. The bikes are 2005 models with mid-level 7 speed Sram shifters. Almost all of the shifters are original equipment, and still work relatively well. I don't know how many classes of 5th graders have used those bikes before we inherited them from a neighboring city, but it has been a lot. At that age kids can be petty hard on equipment. Loading and unloading the bikes from the trailer is also hard on them. As djb said, changing cables cables can be a little tricky.
