I can't answer your other questions, but about how good 10g is... it's amazing. Oracle is hard to set up and frustrating sometimes, but it is also an incredibly powerful database, way ahead of anything else.
I'd recommend picking up some books by Tom Kyte. I'm reading his most recent now, but I'd recommend starting with
Effective Oracle by Design
http://www.rubick.com/bookshelf/book-view?book%5fno=130
It's pretty advanced, but really gives you an idea of how you can take advantage of the database..
