Einstein, I'd say, was at least a weak atheist(his view on a 'personal god' and religions in general are quite clear, he regarded them all as childish superstitions). He has some funny quotes on religion. Though most scientists seem to stick with agnosticism(which is basically the same as weak atheism), which is more than fair.
Any scientist who claims otherwise is probably not worth listening to. As they've failed to apply the scientific method.
He clearly stated he did
not believe in a personal god, souls, heaven/hell, divine miracles, or any sort of god which plays any role in human life, fate, or destiny. Not that "
I'm unsure of whether there is/are god(s) or not", which is true agnosticism. That's not even close to what Einstein ever said.
One could say... that God to Einstein was Nature. Laws of the universe, matter and energy(existence), and spirit(thought, actions, morals, ethics, etc.).
He even claimed belief in Spinoza's God(which is not really a god at all, but a philosophy):
http://en.wikipedia.org/wiki/Spinozism