Mac Specs: 1.67 Ghz 17" PB w/1 GB Ram; 400 MHz PM G4, 366Mhz iBook Firewire, Nano 4GB Black
I've had problems with all my macs and ejecting CDs. I've found usually it works, if I drag the CD icon to the trash. Using the button on my keyboard does work about 70% of the time.
If a CD is ever "stuck" in the drive, you can reboot while holding the mouse/trackpad button.
Mac Specs: Mac Pro 8x3.0ghz 12gb ram 8800GT , MBP 2.16 2GB Ram 17 inch.
I have had the same problems with my power book... I am still working on an easier solution (been trying to look around the internet for reasons why this happens) but so far the only solution I acutally have is that you reboot the computer while holding the trackpad button down as rs2 said.