The w580i will work over bluetooth with a macbook, and really all that will give you is the ability to transfer files and I think contacts(though i havent tried yet). The Sony Ericsson Software is over rated, not to mention if you got the USB cable with the phone, you can set your phone to be a USB drive for you memory card. The music player software intigrates directly into the “Music” folder on your phone and the memory card, so there is no need to really use the PC software any ways. On a unrelated side note, the phone in addition to supporting dozens of music formats (mp3, wav, wma, mp4), it can also play back 3gp video content at 30fps without even breaking a sweat, so it could even be an OK video player in a pinch. Hopes this helps.
BTW, I Love my w580i I only got it a few days a go and really cant wait for my memory card so I can put some real music on it. [I HATE 64kbps audio :( ]