Thanks for the info. I've been thinking about getting an oiler (or building one) for sometime now, so this comes in handy.
A few general questions:

1) How does an oiler copes with offroad conditions (desert sand and dust in the summer, mud and water in the winter)?
2) What about the outside of the chain? When I was too lazy to clean and oil my chain (which I usually am) after a riding in water, the outside of my chain developed a bit of rust. This was clean by oiling the chain. Will an oiler do the same thing, or will I still have to clean my chain the old fashion way?