I wanted to replace the optical drive with an SSD.
The upgrade went well. The instructions were very clear, however I was a little agitated how the re-assembly instructions were just "do the steps backward," as that wasn't quite the case. I would love to see the re-assembly steps included on the otherwise awesome guides.
One hiccup in the install was that I was unable to screw the four T10 Torx screws of the plastic rail that was originally attached to the optical drive to the SATA hard drive enclosure (Step 22, re-assembly). The enclosure was simply too long and the screw holes did not line up in the two pieces. The SSD seems to be held in ok without this piece attached, but I don't know if this will pose a problem in the future. Thankfully SSDs are lightweight.
As to the outcome, the SSD is working well in the iMac EMC 2266. One thing worth noting is that the drive has a negotiated link speed of 1.5 Gbit/s instead of the full 3.0 Gbit/s. I am not sure if this is a limitation of the optical SATA port or if this is a configuration issue. YMMV
Get a Spudger if you don't already have one. It really helped.