Me neither, I'm pretty OCD set in my ways. It helped me to find two shampoos that I like so I can switch between them periodically. Anyway, I don't know if it's (http://hairloss.instah.com/hair-care/does-switching-shampoos-help-your-hair/) an urban myth or anything, but on the other hand, it'd seem weird for shampoo companies to broadcast "Please to be using our competitor's product now and again for maximum results!"

Also, leave-in conditioner is magic, I've found.