Yesterday, fellow blogger Steve Sande hopped into the TUAW backchannel all fussed. As part of some iMovie troubleshooting he was doing with Apple's support wizards, he was trying to get his new iMac to boot into the recovery partition and was getting nowhere. Holding down the Option key during reboot wasn't showing the volume as an option the way he expected.
Has this happened to you? Well, there's a reason the recovery partition didn't show up -- Steve was working with a Fusion drive-based system.
We started by checking that the disk contained the recovery partition.