As you may have heard on RFN, I was initially underwhelmed with Rondo of Blood. And I recently started replaying Symphony of the Night for the dozenth time, leading to some unflattering comparisons. But I felt like this game deserved a better chance, so I went back to it in the past couple of days. I finally beat Death after several tries, which was quite satisfying (especially his defeat animation). I had to look at a FAQ on how to unlock Maria, but it was so worth it. She plays much more like Alucard from SotN, with vastly improved mobility and a seemingly endless variety of sub-weapons. I have also been impressed with the array of secret rooms, secret exits, and secret levels, even though I haven't tried any of the latter yet. There is definitely a ton of replay value in this game, which you couldn't say for any other classic Castlevania games.
I'm starting to think that if you were already a big fan of Castlevania from the earlier games, it's clear that Rondo of Blood would be an amazing revelation. If you got into the series with Symphony or later, it's harder to go back to this style and appreciate the little refinements that Konami put into Rondo. But my personal experience is improving greatly as I spend more time with it, peeling back the layers to discover all the great content hidden away.