Hi List Just to let you now: jpilot works perfect with my TREO 270 usb.Make sure you done modconf and then USB serial adapters (usbserial, visor must both be in the kernel).
Then do modprobe usbserial visor. Then press the hotsync button at the TREO and then press sync in jpilot. And then enjoy the magic of Linux. Many thanks to the jpilot mailing list. Zeno