I've had my 211 for about 3 weeks now. At first, the caller ID seemed to work ok. Now it seems that just about all incoming calls are showing up as name "unavailable" & "out of area". I haven't been asking the callers what service they are using, but they have been from landlines & cell phones and the calls today have all been long distance. My other landline phones in the house all show the correct caller info.
I don't think this is strictly related to calls from Cingular service, at least not in my case.