I got started using the surplus powder just about the time most of the better ones dried up. I wasn't interested in but two of them at the time as I was loading a custom overbore magnum and the loads were developed using the WC-872, so that is what I got as well. In most calibers it burns like fine ground coal, but in the big case with enough bullet weight in front of it, it performs admirable once the pressure is up to snuff.
As mentioned each lot is to be respected and worked up to accordingly.
After finding the 872 to work out as well as it did, I picked up some 860 as well, for use with my mid sized magnums, and it has worked out in similar fashion with the heavier for caliber bullets. I have found it is a bit more finicky to work with, but does produce some nice accuracy and groups out of a couple of my magnums, and like the 872, for the price I got it for in comparison to commercial powder I ain't complaining.
The last two I picked up were the Russian Salut and WC-297. Both of these have proved to be equally efficient and for the price I got them for very well suited for my uses. I only got one order of the Salut before it was gone and wished I had been able to get another, but I already had a big jug of Hercules Unique and am still working diligently to burn it up. The Salut is almost a direct cross over in weight per charge as my can of standard Unique so it has been easily added to my load database.
The WC-297 has been fantastic to work with. The lot I have is a bit slower than the commercial Win-296 I had been using for several years. I was just about to run out of it when I found the price difference in an 8# jug significant enough to give it a try. I figured getting 8# delivered even with the hazmat for half the price of the same amount of Win-296, would be worth at least giving it a looksee, and besides it was in stock and the other wasn't to be found. As such I have had no issue what so ever working up loads with it to duplicate my standard loads in .357, 41, 44, and 454. I haven't tried it in the 30 Carbine yet but feel it should work equally as well.
This said, no mater if you decide to go with the surplus or canister grade, you should compare the prices, and load compatibility, and decide accordingly. It will do you no good to have a surplus powder that your only able to load one caliber with unless it is a specific fit that nothing else will work in. As for a varied caliber powder like the 844, 846, or some of the others, well I agree I am more apt to simply go with the commercial grades since the prices are so close.
Mike / TX