Don't want to be a dark cloud or anything, but I don't like it. He looks too dull and grey.
Stormtroopers in the films look shiny and white, more like how the pre-paint started out. Even the dirty ones on Tatooine look whiter and shinier than yours (they just have patches of red dirt here and there). Yours just looks kind of grey. I know white is hard to do and all, and I'm not saying I could do better, but I think the pre-paint looks better as a Star Wars Stormtrooper.
I think you're better off just putting some nice basework on the pre-paints and leaving it at that. Stormtrooper armour is shiny white plastic, so perhaps the best way to convey that is to simply leave them as shiny white plastic?
Sorry, I really don't like being a downer, but that's just my opinion, for what its worth (not much really).