This is from the release notes in the OP so people don't keep posting what works and what doesn't...
CM10 Release Notes
The most up-to-date list of issues in on our Google Code page.
camera: Camera and Torch do not work at all
wifi: Clients cannot connect to wifi tethering if WPA is enabled. Use Open for now.
lights: Capacitive lights may not come on if BLN is enabled
lights: If BLN is enabled, it may be disabled on the next reboot
radio: SMS longer than 160 characters will get split and not reassembled by the other side
radio: SMS messages sent too close together in time will not be sent
radio: "Use only 2G networks" option in Settings does not work
radio: Changing "Preferred network mode" in Settings does not work
radio: On Rogers, you may have no data without inputting your APN
radio: Contacts on SIM card are not accessible
radio: Changing call forwarding from this ROM is broken
peripherals: MTP mode does not work on Linux or Mac - stick with USB mass storage for now
NOTE: CyanogenMod does not support syncing your contacts with Facebook. There are 3rd party apps that give this functionality, however.
Alpha 1 - 7/28/2012