I agree with everyone here...
I have not yet experimented with Overdrive, mostly because I have a Kindle and I am uncertain of the availability of books through my local library or converting them.
I am one of those, though that doesn't really like to buy a book unless it's a keeper, yet I am also one of those that does enjoy ownership... I walk a tightrope right now with the Kindle because I am definitely buying and experimenting more (bargain books, free books, etc) than I ever did in the past (avid library user, borrow from family, etc.)
Buying is definitely easier with the Kindle as is storage. A hard drive is always roughly the same size, and I think it is mostly bookshelf space that drove my habits before.
Never-the-less, I like the idea of libraries because I tend to read most books once, at least from the fiction side of things and could benefit financially of using the library more. Yet, I've found some wonderful books thanks to the bargain and freebies and will likely do the same once I try the library out more myself.
Last, I am curious about the S.F. Library mentioned as I am a California resident, and I imagine that their selection far outweighs what is available to me in Yolo County.