I signed up for the $3/mo "Skype Out" (unlimited calling to US/Canada PSTN), and it allows you to use your cell phone's number as the caller ID...nice.

If you want "incoming calls", there was some 50% off for 12 months for $30 "for the year", rate/sale, but you get a new unique number. So it would actually be $66/year for unlimited in/out.

I'm in the DC/Baltimore corridor, and have both AT&T and T-Mo, and on AT&T Edge, there were some QoS issues, despite being in a "full bar" area. This from a Cisco VoIP engineer, calling another Cisco VoIP engineer, who has a Nokia e71, and multiple SIP clients. I made another call to him, via WiFi, and was told the issues subsided.

On T-Mo, Unlimited Talk is $49/mo vs. $29.00 for 500min. In order to get unlimited via Skype, and cheapest T-Mo plan, it would be ~$43/mo.

I'm doing the 500min/mo, plus "Skype In" for the extra $3, and just let incoming calls go to VM...its all about what works for you.

Ultimately, if you have both home and cell phone service, I think the most efficient, cost effective way to go is:

- SIP provider where you get unlimited calling and they provide you SIP settings for any device (unlike Vonage ) like callcentric. $25/mo

- T-Mo (if their coverage works for you) $29.99/mo 500 minutes...or go data only if possible. Data = $10 or $25.

- Configure callcentric on the 900 and make all the calls thru the SIP client.

Total "phone" costs for both home and cell are $65/mo or $80/mo....depending on which T-Mo plan you get.