Although it can be a bit punishing at times it's still a great Castlevania game with a RPG twist.
Simon is a pretty undeveloped character though. He doesn't speak at all and over the course of the game when you get closer to collecting all of the parts and burning them there's no apparent transformation going on with him. He'll talk to many people, buy items, kill a bunch of demon/monster things, rest at the local church, etc. but yeah, nothing really happens to change his character. This however is forgivable as most Castlevania games suffer this flaw, often resorting to game manuals to explain any sort of backstory. They are usually more action oriented games with little plot development.
However Castlevania II sort of breaks this mold by including some RPG gameplay elements. For example, your character levels up, you go into towns to talk to people and to buy items with money you obtained from killing monsters, you rest at the local church to recharge your health, you upgrade your weapons (the flame whip is awesome), you buy more ammo, etc. It even uses a day/night cycle, which, for it's time, was pretty innovative. So in this Castlevania it won't be a non-stop romp to get to Dracula and kill him. Instead, you'll be going from town to town, mansion to mansion, collecting Dracula's body parts which will, at the end of the game, be burned.
What I personally didn't like about it though was it's difficulty. It can be really punishing at times, especially when it requires whipping monsters while doing tricky platforming. Also, some of the game's hints to finding the different mansions are inadequate or are completely lacking. Needless to say, you're pardoned if you decide to use a walkthrough to complete this game.
All of the flaws though are pretty minor compared to the game's overall fun value, especially if you're a new or old Castlevania fan. And if you really happen to like it, it has multiple endings to give it replay value.