I am a coaster enthusiast; however, I can't say I'm wild about most of Knott's coaster collection; not because they're too rough (I wouldn't call a single Knott's coaster rough right now, including Ghostrider), but just because I don't think a lot of them are that great. I do love Ghostrider, Montezooma, and Hangtime though!
I've never had an issue with cleanliness.
I do go mostly for the Mine Ride, Log Ride, and Ghostrider, but I do really enjoy the atmosphere and entertainment too. And while there are a number of rides I don't get on much or haven't been on, period, I always forget how many rides they actually have. They really are like Disneyland in that they have a lot of rides and other worthwhile things packed together in a small space.
It did take me multiple visits to warm up to the park, and as much as I love it, I'd still be hard-pressed to say if it's truly better than, say, Silver Dollar City or Dollywood. But it's a park I very much enjoy visiting, and I can't picture visiting Disneyland at this point without stopping by. In fact, I've been to Knott's more recently than I have DL (for Scary Farm), and I live in IL!