Ok--I'm back
Dan, you seem to be asking two questions here. The first is:
Is Judaism a religion?
I'd answer absoloutely yes. It may be more than a religion--arguably, like Hinduism, it's also a civiliazation. But it isn't less than a religion.
It's a religion despite the fact that we have no creeds and despite the fact that, while we have lots of theology, we don't demand assent to any specific theological propositions. Judaism simply doesn't put the same emphasis on belief that Christianity does.
But although we don't have creeds, lots of other things bind us together: our stories about how God interacts with us (whether or not we believe the stories) our Scriptures, our traditions, etc.
(Sometimes I think all religions come down to entering into a particular story--and by story I don't mean 'untruth.' A Jew enters into the story of the people Israel and Israel's relationship with God. She identifies with that story to the point that, in some sense, she stood at Sinai and accepted the Covenant. A Christian enters into the story of Christ's death and resurrection. She identifies with that story to the point that she even partakes in that death and resurrection.)
To determine whether a person is a 'good' Jew, the question is not: "Does he believe in God and the Covenant?" The question, rather, is, "Does he fulfill the mitzvot (commandments) of the Covenant?" That's what I mean about deed being more important than creed in Judaism.
Different branches of Judaism disagree on what mitzvot he should fulfill. Everyone's on board with the 'ethical' mitzvot--like loving your neighbor--but not everyone agrees on the 'ritual' mitzvot--like observing the Sabbath and keeping kosher. (And there are further arguments over whether or not you can neatly separate ethical and ritual commandments in the first place...)
One of our commandments is to love the Lord our God with all our hearts, minds, and strength. 'Love' has numerous connotations here. While devotion can be part of it, you can also show your love for God by doing what He commanded, regardless of whether you can bring yourself to believe in God.
And that leads me to what I think your second question is:
Can an observant Jew who is an atheist or agnostic be considered a religious Jew?
Judaism says yes. Again, the question isn't whether or not the Jew can bring himself to believe in God. The question is whether or not he's fulfilling God's commandments to him.