I experienced carb ice in a lycoming O-320 equipped Cessna 172 one day right after takeoff, while in a full power climb when I'd just reached about 1500 AGL. Got my attention quick. When I pulled the carb heat, the engine almost died when it melted and swallowed the slug of water. I was a freshly minted PP-ASEL with about 70 hours under my belt then. OAT was in the upper 40's and humidity was really high. Then I owned and flew a Cherokee 140 with an O-320 for about 10 years and never had a hint of carb ice in that plane.
In my RV-6, knowing that its carb heat pickup off the front exhaust crossover pipe is very wimpy at best, I religiously run carb heat whenever I suspect conditions might favor the formation of carb ice. The reduction of power is miniscule in this plane with carb heat full on, and I'd rather be safe than sorry.