If they are all on AM2, then cold. If 939, then lukewarm.
The 939 market is the only market it makes sense to go with AMD, because of the existing install base. 65nm would only really matter to OCers and maybe HTPC builders, of those the OCers being the real market - they tend to buy multiple chips. Not many will move to AM2 to OC, if you're going to change sockets, you might as well go 775 and get the C2D.
What is a benefit for AMD either way is that they get more cores out per wafer, and can make a higher profit than they were before (or lower prices more to stay competitive with C2D).