35mm is all i can afford, but you really can push it if done right! I had over exposed a negative which i proceeded to develop in rodinal at box speed and that mistake was made instantly obvious once enlarged! 35mm is cheap, fun, and what is better than watching your print appear under the red light? (i hope a colour safelight at least lets me see that). The only downside, as my friend whom does 120 and 4x5 tray processing told me, is any scratch, loss of emulsion or defect is more lethal on 35mm than the larger formats. Only last night me and my friend shot a roll which had water marks after drying.... so he proceeded to wipe them off on his T SHIRT! the scratches added a lovely effect to the darkish sky at 5x7. (I had gone up the side of the abandoned factory, up the fire escape and up a ladder and i could see alot of the town from up there, so i shot a few shots! These i push-processed. 35mm rocks although i do want to give the 120 format a try once ive completely found my feet, but I don't see the point really until i start doing giant enlargments. A4 is about as big as i will go for a while until ive completely found my feet. ISO25 is bound to give you grain-free if used properly at ISO25. So to sum it up? cheap, fun, easy, great for starters or professionals alike.