I was pretty happy with the old version of blogger, but I upgraded today so I can use the new API against my own blog. So far I have 4 spam comments (captcha is still on) versus about that number for the entire life of my blog under the old blogger. Bleh.
Could just be a coincidence. I hope so.
(Update Feb 26: A month later, I've had just one more spam comment. So it probably really was just coincidence.)