Keep in mind, the Mac Blu-ray player app
does not display menus! Your standard Blu-ray menu (for whatever reason) is not shown in the app. You are brought to a generic screen that lets you play the movie, go to a chapter, or go to 'other titles'.
While this is usually fine to play a film, if you're trying to find a bonus feature or something specific, you are left randomly clicking on 'other titles' and guessing the item you want to view depending on the length of the feature. Also, when you click on an 'other title' item, after that item is done, you aren't brought back to the generic menu. You must open the disc again, wait for the generic menu to load and the disc to spin-up, and make your selection again. This can be frustrating if you're searching for a certain bonus feature, etc.
I'm sure they have a good reason for not rendering the menus. I'm unsure if it's a technical issue or a licensing issue, but either way, it's something you should be aware of before purchasing the app. From what I've seen on their website, they don't even seem to mention this issue. But I'm still looking...
I'm happy enough with it, especially considering the price I paid. It works well on my 2011 iMac running Lion with an external BD-ROM drive connected via a cheap, but effective USB 2 to SATA adapter.