They work great for me. I use fairly light loads, between 2-3/4 and 3 drams of FFg and an ounce to 1-1/16 oz shot. Large pistol primers fit and work perfectly. RCBS sells a 12 gauge shellholder that's not in any of their catalogs, but if you call them they've got it.
The cases will stain after the first firing pretty much no matter what you do, but if you wash them (inside and out) with _cold_ water shortly after you shoot them it minimizes the discoloration.
I've used Duco cement (the fumes are awful!) and Elmer's carpenter glue for the top wads. Both work great, but I prefer the less stinky Elmer's.
BP generates an enormous amount of heat! Take a glove for your 'forend' hand and be careful handling the cases right after they've been fired.
BP also generates an enormous amount of fun! Be prepared to have everyone around you ask to shoot a few...
