A few years ago I purchased a 3.2 pound Swedish pattern forging hammer from a conference vendor. At home I tried using it and was disappointed and soon quit using it altogether. Then a year or so later in August, 2004, I was at the Rocky Mountain Smiths conference and watched Nol Putnam use a similar hammer very effectively. At a break I looked closely at his hammer and noticed that the cross peen was somewhat mushroomed which softened the sharp radius a lot. I asked him about it and found he had intentionally made the modification and liked it.
At the time I couldn't quite remember what I found dissatisfying about the hammer but decided to check it out. Back home I tried the hammer again and the face seemed to work fine but the cross peen was so sharp it was too severe to use in the manner I usually needed. So, I decided to modify it and try again.
I heated the cross peen with the torch a few times and struck the anvil until I felt it looked about like Nol's. I'm just guessing, but I think, the radius changed from .25" to 1.5".
That seemed to make all the difference in the world in the usefulness of the cross peen and today it is my most used forging hammer. Subsequently, I purchased two of the 2.2 pounders and modified them in the same manner.
I'm a believer in keeping the hammer and anvil faces smoothly dressed and have a linear bench workstation set up for touching up the hammers and other tools - bench grinder; belt sander; Scotch-Brite silicon carbide deburring wheel; hard felt wheel with polishing compound. A 120-grit flap wheel on an angle grinder works well on the anvil face.
I have made hammers and have helped students make their hammers, but now it seems to be nice exercise in craftsmanship but not a cost efficient practice for me and I might never make another. On the one hand, my hammer assortment is considerable and, on the other hand, those who specialize in tool making can make a nice hammer for $35-$40 and I can't, if my time is worth anything. Business is business, time is money and all that.
At this address http://www.anvilmag.com/smith/blcasabs.htm you can find "Blacksmithing as a Business" by Nol Putnam. It was published in ANVIL Magazine, January, 1996.