Castlevania IV should mostly be a breeze for you after I-III. (I am curious, what do you think of Castlevania 64/Legacy of Darkness? (since it sounded like those were your first games)
I kinda liked the N64 games. I mean, they had Frankenstein chasing you with a chainsaw through a hedge maze garden, it couldn't have been TOO bad. But I remember the camera and controls being crap, and the fact that it looks so ugly today kills any interest in returning to it.
Anyway, beat SCIV today. I'll try a little different and break it down into pros/cons:
Pros:+When it comes down to Classicvania, this is the best one. It takes the original games, injects steroids, and lets it fly.
+Solid soundtrack
+pretty good art direction
+Lengthy for a Classicvania
Cons:-Swinging isn't that fun. It doesn't help that I played this almost directly after the incredible, seamless swinging of Bionic Commando Rearmed, but SCV4's swinging is slow, rigid, and gimmicky. The Mode 7 swinging room was little more than an excuse to "wow" gamers with its rotation effects.
-I'm still not a huge fan of Classivania's style of play. Yeah, its more challenging than the Metroidvanias, but that's because Alucard and co are so nimble and smooth. Simon still feels like he has cement blocks tied to his ankles and still has a god awful jump. When I jump and land in a bottomless pit because Simon can only hop 6 inches from the ground, its incredibly frustrating and the opposite of fun
-The 8-direction whip actually works AGAINST the slow, methodical feel of the Classicvanias. it reduced what were dangerous enemies that required a steady approach and careful tactics to surmount to rote moving targets, since most enemies couldn't get around it. And without that challenge, what was an otherwise necessarily slow and steady approach lost that meaning and often became a pointlessly slow lurch. Congratulations Konami, you totally missed the point.
Overall, I did enjoy SCV4 more then the others(although its ranked closer with CV3 than the others), but I have no idea why people think this is the best of the series. All I can think of is the "Final Fantasy 7 Effect", where I play it see an ugly as hell, poorly-translated, above average RPG with God awful pacing. But perhaps had I been there when it was coming out, I would have fell in love with it. Not that I'm saying people who love SCV4 are blinded by nostalgia, but I vividly remember after beating Dracula and staring at Simon as he watches Castlevania fall, and I just couldn't help but think, "Why do people think this is a great video game?"