As a Mac and PRS505 owner, I can tell you that you will have no problem.
The 505 will appear as a USB drive in the Finder, and from there you'll be able to drop any ebook file into the device.
Moreover, using Calibre, you'll be able to convert them, manage them in a nice, tidy, iTunes-like library, and upload them to your device with full metadata. Calibre is way better than the provided Sony software.
The only problem you'll run into is reading DRM'd books. For this, two solutions :
- you can strip the DRM of eReader, Microsoft Reader, and Mobipocket ebooks quite easily (recently, someone on this forum explained also how to circumvent the ePub protection Adobe invented)
- you can install Adobe Digital Editions on your Mac (it's an AIR program, runs anywhere) and use it to manage the DRM'd books
- you can install the Sony Reader software on a Windows virtual machine, or even Bootcamp ; I know that people recommend not running the Reader software in a virtual machine, and for the flashing of the firmware, they are right ; but for "normal" operation, like buying books and uploading them to the device, it works !
- there's no 4
Let me know if you need help !
Cheers,
David.