Coasting in gear will probably save fuel. I lost FE when coasting in neutral (automatic trans) because apparently there is a fuel cutoff in my vehicle. It actually burns fuel when in N instead of not burning when coasting in D.
Also, I don't know if going into neutral is too good for your tranny, I made a thread about that and it had mixed answers.
http://ecomodder.com/forum/showthrea...anny-1153.html