I went to see it tonight. It was mostly OK, some good action scenes but often things were moving too quickly to really be able to appreciate it. I found myself wanting to watch Ong Bak,the super-awesome Thai movie starring Tony Jaa. It's super-awesome because there's no wire-work in it. I dislike wire fighting. If you're going to do it with wires, you may as well just do it with camera tricks or CGI and then even I could do it - not awesome at all. The stuff Tony Jaa does in Ong Bak is just fantastic and - more importantly - surprising and often funny.
Aaaaaanyway. Blood is essentially Blade but instead of Wesley Snipes the half-vampire vampire killer is a Japanese schoolgirl. What could possibly go wrong? Mostly nothing goes particularly wrong or right. Add in an unsatisfying ending and you've got "meh".
I would have been annoyed if I hadn't managed to get to it but I'll have forgotten about it in a month.