Interesting... I pretty much think along the lines of AdD.
This was discussed a bit in the "fallen angels" thread on the mysticism forum, but suffice it to say that I think of it more like the Jewish notion. Satan, which to me is a symbol of our own inner temptation and "demons" of hatred, fear, ignorance, etc... is only there because God created it to be there. Satan has a purpose, and that is to test or moral fibre and for us to grow spiritually and learn to lean on God. I don't see Satan as a personal spiritual entity so much as a symbol of that which is in us.
I also define evil differently than most. I think sin is "missing the mark"- making mistakes, which everyone does. That's part of being on earth- fallibility. Evil, to me, is neither making mistakes nor the natural cycles of this world (death, famine, natural disasters, disease). Natural cycles are just that, they are natural. It is only our perspective that makes them bad or evil. Really they are there for a reason, and I choose to learn how they operate and embrace those cycles, while attempting to alleviate suffering rather than thinking they are somehow tied up with the Devil. Evil, to me, speaks of knowingly harming someone. It is being malicious and taking pleasure in others' suffering, spiritual stumbling, etc.
The Devil, to me, is a symbolic representation of the temptations that are in all of us, and were created by God. When I read Revelations, for example, and Satan and his demons are cast into the lake of fire, I see this as symbolic of a new world in which we are all in the constant presence of God, and have shed our temptations to harm one another and ourselves. Without these temptations we would not learn or grow spiritually. Without pain and loss and suffering we would lose out on lessons that teach us forgiveness and hope and finding strength, peace, and joy in the eternal Divine.