So far I haven't seen anything I don't like about the D600. It will make an excellent companion to my D800 and will be a great tool for wedding photography.
In some ways I can see myself using it more often than the D800 simply because of the weight advantage and also many of my clients simply don't need 36mp.
Historically, I've avoided "pro-spec" cameras such as the F3 (in days of yore) preferring a FE2 or more recently a D800 instead of a D4 simply because I don't like heavy camera bags and like to work with smaller cameras (despite having huge hands!). So the D600 seems pretty good to me.