Oh good grief. I hate going on work trips in the middle of discussions like this. OK, I'm not quoting, but a general answer:
The reason why agnosticism is different than atheism is precisely because agnoticism includes agnostic theists and agnostic atheists. Whereas karajorma seems to think the second word is the primary trait, I'd argue that the first word - agnosticism - is actually the more important one.
Focusing on whether or not an agnostic aligns primarily with theists or atheists puts the primary debate on the existence or non-existence of supernatural entities. Conversely, putting the emphasis on the 'agnostic' part is a matter of philosophical view of the world.
The reason I keep referencing Heisenberg and Schroedinger along with philosophers is because - in my view - agnosticism of both species shares a common method of viewing the world that is inherently rooted in the scientific method; contrast with atheism that asserts a firm lack of belief in deities or supernatural powers. Since we do not know and cannot know, we are very much sitting in the scenario Schroedinger premised with his cat thought experiment. The evidence hasn't flipped either way (and anyone saying otherwise frankly has an agenda; see my experimental design on page 4).
Agnostics are different from atheists, because all agnostics - be their bent diest or atheist - share a common view that the question of deities is inherently unknown and unknowable (at least in the immediate future; some agnostics believe that extends for eternity, others think the question may be answer one day, and still others aren't willing to call that either). Once again, this is not intellectual cowardice - it's an acknowledgement of the power and meaning of the scientific method. Atheists generally shortcut the method based on certain assumptions because they believe the data leans a certain way. While I certainly agree that atheists generally have a stronger argument than deists, this argument is primarily philosophical in nature and grounded on the observable. While I have the utmost faith (irony alert) in the scientific method, I also acknowledge the philosophical and evidentiary validity of Heisenberg's work, which is very troublesome when thinking about this topic in particular.
Atheists who refer to this view as intellectual cowardice or dishonesty are, in my view, missing the point and tradition of the philosophical roots of science. Which is why I continually refer to myself as an agnostic rather than an atheist. While I believe in challenging the irrational byproducts of religious belief which cannot be substantiated (abortion, contraceptives, anti-homosexual policies, imposition of religious ideology on other peoples, religious conflicts, etc), I do not believe that I have enough information to open the box and see if I need to put some food out for the cat or not. Atheists, on the other hand, have decided the cat is dead and they're going to save money on their grocery bill. This is why position is fundamentally at odds with Luis, karajorma, and the rest.
To use what Mikes (I think) pointed out: Atheists, deists, and agnostics flipped a coin. Atheists think it landed tails. Deists think it landed heads. Agnostics see it still spinning in the air and aren't willing to call it until it gets closer to the ground. I fit in the latter category.
