I gathered a little data today. O-200 in C150M, at 2500 RPM, 58F OAT.
Carb air temp cold air = 42F, apply full carb heat = 62F carb air temp, RPM now 2425. Lean to peak 74F carb air temp, and RPM 2425. I did it three times this way, and in all cases, temps within 2F of those values. If I needed to deice the carb, I would like to have those additional 12 degrees F, which i get just for leaning the mixture.