Perfect should not be the enemy of the good, that's why he is right to vote for the bill. The bill doesn't prohibit a single-payer system, so Kucinich's goal could still be accomplished. Also, Kucinich I think once again can be called a Democrat again. While voting against bills cause they "aren't liberal enough" is nice on the surface, in the end they are voting like Republicans. There isn't a third option to vote for or against something and put an asterisk next to it, it's up or down.
Don't get me wrong, I don't like incomplete, compromised, or watered-down bills, but voting against them is sometimes worse than voting for them.