Nautilus,
I'm glad to hear yours is up and running.
Beckmola,
The only cons that I can think of with a UV sterilizer is initial upfront cost, the fact that you have to keep them clean, and the cost of the replacement bulbs. Other than that, they kill a LOT of the things we don't want in our tanks. Like Ed Hahn said....good insurance.
Here's a link I pulled out of the
RF Resource Library (I tend to spend substantial time in the Resource Library and that's why I put it in my signature).
I have a used 18 watt unit (with a new bulb) but I will eventually buy the same unit that Dave just posted.
The reason that it is important to keep them clean is that if the quartz tube is dirty, you don't kill as much. They also operate best off of low flow so the bacteria/algae/parasite, etc. are in the chamber long enough to be killed. My unit runs off a very tiny powerhead.