What's new in iSync 1.1?
iSync 1.1 works with additional brands and models of mobile phones, allows you to synchronize Safari bookmarks across computers (if you have a .Mac membership), and has a number of performance and stability improvements.

"iSync supports the largest array of Bluetooth-enabled phones of any synchronization software. The latest version expands support for the pioneering Sony Ericsson Bluetooth lineup to include the sleek new T608 for Sprint PCS"

for complete details on iSync

I have installed and try the update on my Treo 300. Works great, and seems to be a little faster, after the first sync.