Not that it really matters if he was. Lots of really intelligent people believe really odd things. Take my doctor...out back and beat some sense into him. But really, if you want to use Einstein as an example of a great scientist who was also a believer, you are going to have to explain this letter.
“the word God is for me nothing more than the expression and product of human weaknesses, the Bible a collection of honorable but still primitive legends which are nevertheless pretty childish.”
That really doesn't sound very christian to me. In fact, I would say that he is at least as much of an atheist as I am. He consistently described himself as an agnostic but our views on god are identical. I just happen to feel that the word "agnostic" is nothing more than a soft way of breaking it to folks that you don't believe in their imaginary friends. I plan to write about the semantics of agnosticism vs. atheism later when I feel like I have it figured out a little better myself.