Sonic 3 is where the series started to go downhill.

[Sniffnoy]

For that matter, IIRC, it's pretty easy to get past it as Super Sonic without knowing the trick. Of course, I wasn't able to get Super Sonic by that point back then...

[DackAttac]

You were able to get through the infamous drum of Carnival Night 2 on the first try, Flash? In fact, did anyone here get through it on their first try?
I also got stuck really bad in Sandopolis 2 back then.

What got you? The fact that the level is full of instant-deathtraps or that one stretch of sand-falls where you have to jump from one to the other and then jump on a 180º pivot-platform somewhere along the line? Because the latter had me stuck just as long as the drum... except when I replayed it, I forgot how to do it. I don't think I had that shit nailed until... God, Mega Collection, really.

[FlashTHD]

I forgot if I got to the CN drum before I got S&K, but I never got through it legitimately until I read how on the internet years later. Until then I thought Tails tagging along in the act whether you liked it or not meant you needed him to make it.

...it's a slight bit embarassing but the ghosts in Sandopolis 2 are what kept me from that one at first. Same reason as the Angel Island flames. Eventually I conditioned myself to scramble through the act as Sonic or Tails as quickly as possible so the lights wouldn't completely go out. Strangest part: they say Knuckles' game is supposed to be harder, and the ghosts are all over the place in Sand2 to begin with, but first Sonic game I beat (first game ever, even) was S3&K with Knuckles...with all the Super Emeralds. So the little things that held me up yielded me year(s) of practice at everything else.

[Oompa Star]

I never really liked going through Sandopolis Act 2 unless someone was sitting next to me. Lava Reef's boss sequence really had me frazzled, what with the Death Egg up in the background and indirect method of fighting Eggman.

[Isuka]

What got you? The fact that the level is full of instant-deathtraps or that one stretch of sand-falls where you have to jump from one to the other and then jump on a 180º pivot-platform somewhere along the line?

The sand-falls, of course. I don't remember if I got through the first part of Labyrinth Act 3 in the first game before reaching this point in S&K, maybe that would have prepared me in some form.
I learnt how to pass the drum by myself... well, while in a fit of controller-hitting and game-cursing rage, after several minutes of trying everything I could think of.

I never really liked going through Sandopolis Act 2 unless someone was sitting next to me. Lava Reef's boss sequence really had me frazzled, what with the Death Egg up in the background and indirect method of fighting Eggman.

Ever played a Super Mario Bros. 3 castle alone, in the darkness and with the volume up? And I also tried to smash the "Hot Mobile", only to fail miserably and blame the fucking game for my own fail.

[The Ghost Of Ember]

Ah, the CN Drums. I remember it took me a good hour or two and several dozen attempts before I finally figured it out. Initially I used the water shield trick oompa described, which always inevitably backfired on me. But I did eventually figure the trick out. Maybe it's because at the time I had all the local neighborhood kids crowded in my room helping me. That was the first time I beat a Sonic game too. In front of an audience. Well, the two or three friends who had stuck around anyways.

Am I the only one who preferred the Sonic 3 levels to ones in Sonic & Knuckles? I mean, Sky Sanctuary and the Death Egg zone where the only two levels I really liked of '& Knuckes'. Lava Reef/Hidden palace had some great art design, but I wasn't so fond of the actual gameplay. The gas spewing robots still have a nasty habit of killing me. Sonic & Knuckles provided Knuckles and a sufficiently epic ending, but the overall design just felt lackluster to me.

I mean, Mushroom Hill and Flying Battery were so simple and easy as to be boring, and Sandopolis follows suit for the first act before jumping into 'mind bending difficulty' (at least that's how it seemed at age 7 or whatever I was at the time) for the second. And then the difficulty never bothers to go back down. I suppose it makes sense if you consider in the intended product Sonic & Knuckles was entirely intended to be the second half of the game, but it's still somewhat absurd.

[Sniffnoy]

I've always been kind of disappointed that S3&K simply has the Sonic 3 levels first, then the S&K levels, rather than merging them into some sort of "correct" order by supposed difficulty. But I suppose then they'd have to redo the cutscenes and the numbering and it would all be too much work.