Yes, it's interesting that Satan is still very real for Witnesses, and they see at least as much evidence of demonic activity as of angelic activity. Even though they acknowledge that there are two other causes for bad things that happen — chance, and human imperfection — they believe that the Devil is the third cause, though as I got older I stopped seeing why it was necessary in addition to the first two causes to explain things by saying "the Devil did it."
And you know what? He really wants people to stop believing he exists so that he can be more effective, so we're playing right into his hands ;-)
Many of us grew up as JWs imagining that he was watching us all the time. Like Big Brother in 1984 with its omnipresent cameras, he can't read minds, but he can read facial expressions, so you shouldn't let yourself linger for a moment on anything you shouldn't, because he sees where your eyes are looking and he knows when you are interested in something.
P.S.: Of course anyone who adheres to an inerrantist reading of the Bible has to believe that the Devil exists, so the JWs are no different in this regard than other fundamentalists. "But we're not fundamentalist," cries the Witness. "And... what does inerrantist mean? Well, it doesn't matter, we're not that either."