ZENIT has published an introduction written by Georges Cardinal Cottier, O.P., to a book on exorcism. It's a bit disjointed in translation, but there are some interesting bits.
Though he sinned, the fallen angel has not lost all the power he had, according to God's plan, in the governance of the world. Now he uses this power for evil.
I've never thought of the devil's power in the world as being fundamentally the same power God intended him to wield according to His will. But of course it is; it's not like God said, "You've passed on doing My will and have chosen Door Number Two, which has... demonic power!"
The devil is much more dangerous as tempter than through extraordinary signs or astonishing external manifestations, because the gravest evil is sin... A sinner who remains set in his sin is more wretched that one who is possessed.
I admire myself for not being curious about demonic possession and related topics, lest through presumption I leave myself open to attack. Meanwhile, the demons are probably delighted with how open I leave myself to plain old temptation.
Saint Thomas and Saint John of the Cross affirm that we have three tempters: the devil, the world (we certainly recognize this in our society) and ourselves, that is, self-love.
If I had to identify a tempter in my life, I think I would much prefer to go with "the flesh" rather than "myself," which is an awfully personal way of putting it, don't you think?
The Sacraments have in truth a priority over the sacramentals, a category in which exorcisms are included, which are requested by the Church but not as a priority.
We tend to think of exorcism as the elephant gun in the Church's spiritual armory. When all else fails, we put in the call to Max von Sydow and take cover.
Really, though, exorcism isn't so much powerful as very focused, more scalpel than elephant gun, and the exorcist himself draws strength from the Eucharist above all else. And after all, time was the office of exorcist was one step down from the office of altar boy.