Well I guess I'm lucky I bought a sony ericsson. I'm connected via that phone right now, writing this message
The bluetooth link worked so exceptionally fine that I never bothered with the USB cable or IR link. I don't know about sending files though, my Nautilus file manager only has bluetooth file send (which seem to work fine), not irda, but maybe there is some additional plugin.
Anyway, can you talk to it using e.g. minicom? Try issuing some AT commands. To establish a connection, use kppp and enter the phone number *99# and use any user name and password (I think this applies to all GPRS/3G operators, but I've only had experience with three, and only in Sweden). That should be it.