yeah, the AM-SAT button will control the satellite receiver module, but it's yet to be announced XM, Sirius, or both. I'm told 3 weeks. Not holding my breath.
Good luck with the Treo... Mine ( with Verizon and Goodlink) locked up and rebooted several times a day. I run my business from the phone and can't have that happening. Sometimes took 5 attempts for my office mgr to call me when I had a full signal. I have had a blackberry for 4 years and switched to the Treo 650 about 3 months ago. Returned it last month and went back to the blackberry, albeit this time a blackberry with bluetooth. I had to enter those address book manually, but there is a transfer feature (requires blueooth OBEX, which the treo has but not the bb). Oh well. CallerID still passes through, and I can answer and dial from the Nav system.