You should have no problems transferring images and MP3's via USB. You just connect the phone in "File Transfer" or "Mass Storage" mode and then drag and drop the files. Alternatively, you can transfer files via Bluetooth using the Macs Bluetooth File Exchange utility.
On www.feisar.com there is also a whole load of additional information on using Sony Ericsson phones with Macs.
Posted by josh_1090
thanks very much, that's very helpful!