I once had a cellphone that played very nicely with Linux, the good old Siemens S55. Unfortunately, my SE P1i doesn’t. I tried various combinations of Multisync or OpenSync, nothing helped. Today I bit the bullet and installed funambol with syncevolution. What shall I say, apart from having to run a ~250Meg Java Application server just for me, it simply works. Period.
And thanks to Blueman, this works with Bluetooth now, too (Via PAN of course, not OBEX).