My dealings with the 30-30 are just a bit checkered. For starters, I'll turn you on to this:
Ode to a 30-30 Pts I thru III
After that episode, I spent the next few years trying to figure out why I was having poor luck with the 30-30. Mooseboy kept trying the 30-30 and it did not work for him any better. He lost a deer in 2004. In 2005, we had to finish one off. All this while, I really wanted to believe the 30-30 was a good cartridge.
Adobe Walls over at the 24hourcampfire told me to try Winchester 150 gr. Powerpoint bullets. However, also right about then Mooseboy switched to M1 Garand and further load development for the Marlin 336 got shelved. The change to 30-06 changed everything.
It wasn't until this year that #3 son, Angus, came of age and decided to use the Marlin for his first deer hunt. He shot a nice fat doe and I could not have asked for better performance from any of my 30-06 rifles. It took a few years to vindicate it, but I am glad we can put this behind us.
In retrospect, I think the trouble I had from the Marlin 336 was a combination of the kid getting nervous and the various Hornady bullets not expanding enough. My experience with the 30-30 was somewhat anomalous.
The comment has already been made: more deer have been killed by 30-30 than any other cartridge. Yes, and I would also add that 30-30 has caused more deer to be lost than any other. According to a poll here back in the fall, most folks take the majority of their deer within 80 yards. At that range the 30-30 is just as good as any other cartridge, but at 150 yards I do not consider it a match for a 30-06. As long as you know the 30-30's limitations it is a fine round. I would say the same for the 35 Rem and the 44 Mag.
As it is, the Marlin 336 is probably going to be pulled off deer duty either this season or next. Angus has decided he wants to move up to a Mosin Nagant and a deer load which I have downloaded to 300 Savage levels. The 336 is going to be repurposed as a dedicated coyote killer with 110gr to 130 grain bullets.