goodguy20k,
I've been using my X5 as a mobile phone for a few weeks now with the CF card I got from
Convergent Technologies. It looks just like the AmbiCom card from Mark's link (as opposed to the Anycom card.) The voice quality has been fine to me and while the data might not be the quickest thing going I can connect anywhere I can get a phone signal without having to worry about finding a wireless signal. The service I have is through T-Mobile but it did come all in one package (sim card and all) and that was when I opened my T-Mobile account. I'm not sure how they would handle someone with an existing T-Mobile account, but I'm sure they'd be able to do something. The software for the phone is really easy to use and it does pull numbers from your contacts list.