Why do some bad-mouth the 30-30? Because they've made decisions based on ballistic tables, rather than results in the field.
I did that. I finally got a 30-30 a year ago, during 2006 deer season. I've owned/hunted with 30-06, 270, muzzleloaders, and shotgun. I have to say... if I'd started with the Marlin 25 years ago, I'd have stayed with it. My experience is that deer drop faster hit by the 30-30, than by my old 270 - maybe I just shoot the Marlin better. It has PLENTY of power for deer at likely ranges; those who think otherwise, aren't near as smart as they think they are. I hunt in the woods, have never shot anything past about 90-100 yards; I feel confident with the 30-30 to around to my 200 or so (whether I ought to be taking a shot that far is another story).
I put a 1.75-4 Bushnell Trophy on it; works great. Easy to carry - good trigger (better than either Savage I owned) - low recoil/muzzle blast - and it it kills the deer dead. Of the 8 deer killed with the 30-30, I have lost one. The shot was offhand with me breathing hard carrying climber uphill, deer facing me - should have waited or passed on the shot - and I couldn't find him afterward. Found him a couple days later; I just looked the wrong direction. Gutshot - not the rifle's fault.
One buck hit through lungs ran a loop for about fifty yards; a doe hit a little far back limped a few yards, lay down, and was dispatched with a neck shot. Last week, a 5-pt snuck up behind my stand; I turned, he bolted, and I decided to take a whack at him. I fired four shots as he departed, him him once through lungs and another grazed throat; he trotted unsteadily out into the clearcut and dropped.
Every other deer I've shot with the 30-30, has dropped RIGHT NOW and gone nowhere. A 300 WinMag or 30-06 or whatever wouldn't have done any better; all would have been louder, booted me harder, cost more to shoot, and been uglier than Miss Marlin.
I'm keeping her!