calvon - I neck up 8x57 brass for the 9.3x57, then trim to square the mouth. The cases end up a touch too short, but not a concern. I like the 9.3x57 because you won't see too many of them, the style of the rifle itself and it can handle bullets of at least 335 grains without keyholing. I also have a 35 Whelen that is a blast. Cases are easy to find (cheap if necking up 30-06), cast bullets and moulds are also easy to find - but with the "normal" twist of 1 in 16, cannot use the heavier (somewhere over 250 grains) bullets. If you do shoot jacketed, you will have a wider selection (probaly less money also) of bullets in the Whelen. It all boils down to if you want to go through a bit of a hassle to get something that not everyone has. If all you're after is performance, it's pretty hard to beat the 35 Whelen over the 9.3x57 using cast bullets in each.
ratherbefishin' - I've shot 5 deer with the 9.3x57. I hunt heavy woods and brush with a long shot being around 75 yards for me. Use Norma 9.3x57 cases, CCI 200 primers, IMR 3031 (can't remember exact charge), and a Mountain Molds 300 grain cast bullet. I'd guess I'm hitting right around 1900 to 2000 fps. One hunched up and ran about 30 yards and expired with a heart shot. The others did not take more than 3 steps before they went down with solid lung shots. But to be honest, I've had the same results with a 35 Whelen using 220 grain bullets on 7 or 8 deer. Key is the flat meplat used on all my cast hunting bullets. Round nose just doesn't work for me, and I've used them.
I think of the 9.3x57 as a kissing cousin to the 358 Winch, with anything the 358 will do, the 9.3 will do and in some cases better (can use heavier bullets).