I suspect these apply to lots of Sony Ericsson phones, but I know they definitely work with my v600i and I couldn't find them anywhere all together.
- Asking the phone for a non existent file via obexftp makes it very unhappy; apparently often to the point where the phone needs turned off and on again. This is bad.
- ussp-push is your friend.
- To send a vCard (or many in one file) to the phone, do: ussp-push <BT ADDRESS>@5 <local vcard file> pb.vcf. The phone will recognise the "pb.vcf" (in particular the .vcf extension I believe) and ask if you want to import the contacts.
- To send a Java App (ie a .jar file) do: ussp-push <BT ADDRESS>@5 <app.jar> <app.jar>. Again the phone will recognise the extension and then ask where you want to save it - under Games or Applications.
- The normal AT dialup/GPRS command set works fine on rfcomm channel 1.