Our local library system uses Overdrive, which offers most of the library ebooks in ADE only. Since I hate reading on my PC (would rather lie on my bed with the iPod) I have given up on the library and pirate if I can't afford to buy. Only today did I finally download and install ADE. I don't think it will be that useful for me. I only deal with ebooks on my PC if I'm editing/formatting them, which is not all the same thing as pleasure reading
I edit in Oxygen and view the result with Calibre.