I thought that it was an outstanding movie. It is certainly scary, but that is the point! The plot, the acting, the dialogue, the scenes, the camera work, everything is excellent IMHO.
I thought that in the end it was pretty clear that they did defeat evil - although at great cost. Their faith may have struggled, but it held in the end and God used these priests to defeat the Devil. It cost them their lives, but that is a sacrifice that God may call us to make. Why do you think God is absent? There may not be any obvious external signs of His presence, but then there rarely are in anything He does - obvious miracles are very rare occurences outside of specific time periods like the Exodus and the Incarnation.
One of the things I like most about this film is that it shows the Devil as He really is - totally depraved. There is a popular idea of the Devil as a somewhat mischievous, fun loving guy who just wants to stop God being such a stick-in-the-mud. This cuts right accross that, and shows him as un utterly malevolent being who thinks nothing of murder and visiting the most horrible degredations upon an inocent young girl. In the process, the film certainly has some pretty horrific scenes, which is why it has an 18 certificate, and I would not advocate it being shown to anyone younger then that - certainly not younger teens.
God bless,
YN.