I did my initial testing on firmware v1.2.1-004 and CWCID seems to work intermittently on some phone models (Brother FAX-575 fax machine/phone combo) and not at all on AT&T CL2909 model phone. (ATT phone is confirmed as working with CWCID on another device but doesn't work with SPA122). The CW beep comes in but no name/number is displayed.
I was provided a beta firmware v1.3.0-008 which didn't work and then another version named "CWCIDdbg_001_121212_0842" (no real version number) which does seem to fix the issue. In the meantime TAC had posted a newer firmware v1.3.1-003 which is supposed to fix the general instability of this device. That version fixes the stability issues but doesn't fix the CWCID issues. v1.3.1-003 was officially posted on Cisco's site yesterday.
I'm hoping some other people have experienced this issue so that we can have a fix implemented for this in the next release.