I personally like a lot of Epsoma products but I would probably tend to stay away from anything slow release. In my opinion, you loose a lot of control with slow release products, especially if growing autos. There just isn't a lot of life span in autos for the slow release N to come into play. If you are set on using it, I don't think it is going to harm anything as the rates are pretty low at 5-3-3 and the ingredients look real good. Feather meal, poultry litter, green sand, bone meal, alfalfa meal, Sulfate of Potash is all good products and I use almost all of them individually in my soil. The only thing that is slow release is the N so you will probably want to find something to help with growth early on. The CFU's are good also for starting some biological activity. So, you won't do any harm but you are going to need much more than just that to reap a good harvest. Definitely not a one and done product but like I said, if you want to throw it in it won't hurt anything.
Hopefully that helps a little bit. If you are interested in staying organic soil, have a look in the organics section at Eye's or my threads and it will give some idea of some products to use that are reasonably priced. We both do complete organic grows and have had pretty good results.
