A friend of mine and I patterned a heavishot load for the upcoming goose season. We both used Browning BPSs with the "steel-full" chokes screwed in.
We tried Federal and Winchester steel loads of BB to start with, and weren't too impressed with the patterning past 25 yards- there were big holes in the patterns. Next we tried No. 2 Heavi shot and found that it patterned much tighter and denser than the steel BBs and was easily as good at 40 yards as the steel BBs were at 25. The only odd thing was that that the patterns were slightly elliptical (a circle slightly flattned at top and bottom) in both guns. We found the recoil to be pretty shard in the 3" magnums, the Heavishot seemed to recoil more than the steel, but it doesn't matter that much.

The way the stuff looked, a more open choke such as a modified-steel might be in order for ducks, but we didn't bring any smaller shot loads or try different chokes as we were checking patterns strickly for honkers.

After seeing how the heavi shot performed against steel loads, we were both sold on the stuff, whether its worth the extra cost, we should find out in a few weeks when the season opens for us.