Papyrus for Macintosh is among the personal bibliography managers for Macintosh the best and most affordable tool for serious researchers. It's not as easy to use as Endnote, but the richness in features compensates that a few times. Of course you can use it from the very first day intuitively, but you will gradually learn to use shortcuts and benefits over the hours of usage. And looking to the very well written handbook is actually fun. I use this application in Classic environment a few hours daily and maintain a 30.000+ reference collection.