Polycom VVX 1500 - the button backlights don't work when provisioned under RC. In other words, there's no way to tell if it's on Speakerphone, Conference, or Hold.
If the phone is provisioned with the Polycom factory server, or the Jive server, all the buttons light up fine. SP-PHONE lights up green, HOLD lights up red, and so on. Provision it to RC, and bam, nothing.
(The "Do Not Disturb" button works, but I think that's a hard-coded function on the phone, since it basically rejects all calls regardless.)