I also have similar interest. I don't much like to have have certification that is for a specific product (and version!).
IMHO, SOA itself, as a priciple, is not tied to any technology/product/platform. And also, when i look at the test 665 objectives, they cover all the aspects of a SOA effort and I think it will really be a learning experience. So, I am going for it!
But, we probably have to accept that it is IBM's cert, so there will be objectives related to their products. I think this is how we can appreciate the different products strengths/weaknesses.
I also saw BEA's , but they are still working on the final Phase or something.
This is my $0.02.
Guys who already have this certification may have better comments.