To be honest, it was only the contrast with the very thick patch of hair at the front that made me realise that I was diffuse thinning. If all of the top of my head (instead of 90%) was thinning, I'd still have long hair, and would be living peacefully in ignorance... maybe.
I can't really compare too much with the sides and back, because I've been revaged by AA in the past, and all my hair looks shite.