I found C,S,D! to be a fun and refreshing experience. Its pretty simple, very easy to get into, and extremely addictive. Little things get added as you progress (like dating, special challenge tournaments, investments, upgrades and such) but for the most part you just do the same thing from day (level) 1 to day 100. Luckily right about when you start to get over it, you find yourself at the finish line.
I was a little intimidated by it before I tried it, because it looks like it can be one of those frustrating and difficult games, where you need twitch reflexes and expert precision... but its actually surprizingly easy. You do need to be fast and precise, but like: you can't even lose. I went through some days purposefully messing up every single order to see what happens, and nothing happens except for you slowing your progress to the end of the game. That said, don't think its not challenging. If you want to really conquer the game, you'll want to try to get perfect days as much as you can-- and that can be quite a challenge. Also the special challenge tournaments you need to beat for the last few sections of the game are a little challenging, but they are certainly beatable.
I will be honest though, the entire aspect of the game is simply a test of your ability to percieve stimuli and coordinate multitasking of entering codes into a keyboard. That's the whole game. Slowly the complexity of the keyboard codes goes up, the number of things you need to multitask goes up, and little other aspects are sprinkled in to keep your mind on its metaphorical toes. But it's fun. And its fresh and different. I like puzzlers and braintwister games and I certainly hadn't experienced anything like C,S,D! until I played C,S,D! If you enjoy mentally stimulating games then I think you'll like the fresh and enjoyable experience this game provides.