The 640 is a great carry piece. I bought one several years ago for 329 at a gun show. The store price then was around 379. You got a great deal.
After a few years carry, the thing wore holes in all my right front pockets(docker style slacks). I then bought a 642 airweight. I put this gun in my pocket when I get dressed in the morning and don't take it out until I go to bed. I carry it in a Galco pocket holster, which seems to be a good piece of gear.
It takes a lot of practice to be good with one of these. At my weekly range session, I shoot 10 to 15 rounds of reloads that approximate the recoil of my carry loads, Federal Nyclad 125 gr. After 10 or 15 so rounds, I lose interest(it becomes painful to continue). Every two or three months I shoot in a j-frame competition at my local club. The drill requires one hand offhand shooting at 3,7, and ten yards plus weak-hand offhand. It takes me a couple of months to get over the humiliation of seeing my score posted.
However, I always have a reliable gun in my pocket and feel confident that it will help me out of the next confrontation requiring extra intevention until the cavalry arrives via 911.
Good shooting
Jay
