The sensation is lovely, painful, but in a warm, sincere manner. The release of control, or in the spanker's case the taking of control, is fulfilling. The arousal is immediate, the shame/embarrassment fun as a naughty dare.
The expectation and/or giddiness that builds up to a spanking is lovely, the memories of the spanking even more so.
I guess I'm not the best at answering the question except in abstract concepts such as these, but to me its one of the loveliest, naughtiest, frank expressions of physical expression we're capable of...then again I've always been a weird one.
