I've never backed anything on Kickstarter, and between this and Yooka-Laylee it's been tougher and tougher to stick to that policy. But then, it's like, if I wanted to help with the cost of producing your game, I don't want a free copy of it because then what was I contributing to? Nah, I'll just buy it when it comes out and support the creator that way.
It's best to think of Kickstarter as a donation with benefits rather than a preordering a game. I'm with Taelus
in the sense that the kickstarters I've backed are proceeding smoothly but I've also seen plenty of people experience otherwise. I think with Bloodstained, there isn't much to worry about as you have an experienced developer like Igarashi who knows plenty about working with a deadline. Not to mention, this is a high-profile kickstarter like Mighty No.9. I'd be a lot more skeptical if it were a team that had never developed a game before. As for supporting the creator, I guess it's a matter of if you want to support them now (kickstarter) or later (buying the game). Anyway, I lost all interest in Castlevania after Igarashi stopped working on them, so I'm definitely looking forward to this.