I see that some other responses have sprung up since I began to formulate a response to this... but I want to throw in my two cents anyway.
My view is not far from iPsoFacTo's. How Satan is presented changes throughout the bible. Further, much of our cultural mythology about what or who Satan is actually has more of an impact on our collective imagination than what the bible has to say on the matter, itself. This material is frequently read back into the bible: "Oh, Satan - yeah, I know about that guy! He gave Robert Johnson the ability to play the blues! Looks like he's been up to the same tricks ever since he tried to tempt Jesus to trade spiritual authority and power for temporal authority and power!" But, then you go back to Job. Satan is there, too. However, God is actually engaged in some gambling with Satan - not at all the same kind of rejecting stance Jesus takes toward Satan. So, what or who is he? Other passages are also at odds with one another. In my view, Satan is the force that draws one's efforts and concerns into the world of matter - the horizontal - and away from the transcendent world, the vertical dimension of existence. This can truly be experienced as the presence of evil - or the total absence of good - if you descend down far enough. It can cause people to do horrible things and to be filled with darkness. I don't believe my view lessens the reality of Satan - but it does paint him in a different light that offers nuance and, to me, greater understanding.
Also, should one accept the more folksy, "traditional" (is it really traditional if it has changed over and over and over through time?) view of Satan, where does that leave a person with regard to purely academic bible scholarship (that is to say, scholarship not done by motivated believers?). I cannot take the bible as infallible, divinely inspired truth as I did when I was a child because of all the things I've learned about it over the years (a conversation much too long for me to have just now). The whole thing has fallen apart for me as a basis for a worldview because I was originally taught "Take it or leave it! It's all true or it's all false!" And, well, it's not what my Sunday school teachers told me it was. And, now that I am an adult, I see how uneducated and ignorant many of those adults were who I thought were so infallible as a child.
For those embracing the folksy view - I guess you are left having to take the whole shebang. All of us in disagreement are just duped by Satan and bound for hell - and perhaps agents of the devil himself since we are championing an opposing view. There is nothing to learn because you already have the "inside scoop" about all of reality - life is just an experience given by God to test people and see if they'll embrace the right beliefs that will be like the golden ticket to Willy Wonka's chocolate factory in the sky. For those who don't embrace the right beliefs, oh well, they were all evil anyway and deserve to be tortured in hellfire for all eternity!
There are still some remnants of this belief system deeply buried in my reptilian brainstem somewhere, because admittedly, I do sometimes feel a surge of fear about "being wrong" about this stuff - but that's because they got to me as a child and put all this shit in my head before I could even think. The better part of me says that, if the above were true, it reduces God and all of reality to absurdity. It reduces all the rich inner experiences and insights that a person can have to irrelevancies. There's just a big Monarch out there duking it out with some terrifying rebel and everything else is just grist for the mill. That worldview is hermetically sealed. It does not avail itself to reason. It starts off with already knowing the truth - or at least what is most important to know - and believing that anything to the contrary is in actuality just more evidence for the worldview - since contrary thinking is evil, and evil is evidence for Satan, and Satan is evidence for God, and that just proves it all right and back to square one again. I don't see the value in walking down that road.
Anyway, is there objective evil? Yeah, I think so. But does it come in the form of a horned man with a pitchfork who exchanges temporal favors in exchange for eternal torture? If so, we're just living in some Weirdo's comic book reality. I can't sign onto that - and it doesn't jibe with my experience. It also doesn't jibe with the best information we have on the matter.
Like I said, just my two cents.
Satan in the Bible is not the Satan you have charicatured here. Nowhere does it mention anything about horned men with pitchforks. That is a modern cultural overlay. Lots of people are brought up in Sunday Schools and countless other Christian derivative institutions and don't come to the conclusions you have here.
As for eternal hell, that isn't something I personally believe in either.