I popped the game cart into my GBA handheld yesterday to try out the game with the secret rooms for the first time. I'll tell you what, the secret rooms take off some of the pressure of being perfect. They almost balance out the game, in fact. I think I got to Level 4 with 7 continues. And I actually beat the game for the second time in this quick playthrough. (I think my method of beating Dracula Form 1 by jumping forward over his diagonal fireballs and whipping, then retreating a repeating, is different than what most players use). As has been said, once you know about the patterns and adjust to the control speed, it's very doable. (I have found a similar experience with Dracula X SNES, which a lot of people say is very hard, but I find it largely a breeze and one of my favorite pick up and play titles. Even Dracula, who used to give me fits, is very beatable w/ the axes). Anyway, I found playing The Adventure on a portable system like GBA made me feel a little more in control than using the Gamecube controller on the GBA Player.
After beating it again, I popped in Castlevania II: Belmont's Revenge to get a better comparison, and found three things I never fully knew or realized:
1.) A lot of the level design ideas in Belmont's Revenge are take piecemeal from The Adventure. The contracting spike walls, the destroyable large screw that causes spike ceilings to go up and down, the pike platforms that shoot out of the walls, the mad moles that come out of the background, the exploding eyeballs that take out long bridges, etc. Belmont's Revenge was actively seeking to refine what The Adventure did rather than starting over from scratch. Meaning, without The Adventure, Belmont's Revenge wouldn't be all that special. (As if wanting to balance the whip power-down, they made the Punigachi's the only enemy capable of lowering your whip's power, but slowed down their projectile speeds). I saw these things before, but never made the connection in my mind beyond the eyeballs and the ropes.
2.) Because so many elements that were so tricky in The Adventure reappear in Belmont's Revenge, you see that a good chunk of the challenge in The Adventure comes from the clunky controls. If The Adventure had Belmont's Revenge's controls, it would be regarded completely differently, I feel. Belmont's Revenge basically proves that the level design concepts of The Adventure are very well done.
3.) There are also secret rooms in this second game, as someone here informed us, but I don't know if they're quite as well hidden or useful as those in The Adventure. Then again, I didn't find them before I was told, so they were hidden well enough!!!
That leads me to a final thought. I wonder what the original perception of The Adventure was coming off of Simon's Quest. I never quite realized that it was the 3rd official overseas release of Castlevania. When you just had The Adventure, CV1, and Simon's Quest, I imagine it would make for some interesting opinions.