I can't speak to the size of the group, but I would certainly fall within it. For my condition (dermatographic urticaria), the newer drugs (loratadine, desloratadine, cetirizine, fexofenadine) provided very little relief and quickly lost efficacy. Diphenhydramine (and later promethazine, with also has anti-cholinergic effects) provide significantly better relief, are well tolerated (no noticeable drowsiness), and have retained their efficacy over a number of months.

I don't know if this is a common experience or not, but it's not unheard of.