It looks like (from a cursory reading of the patent) that what they have patented is exactly what they've got:
Their squirmy implementation of a quick launch bar.
I'm not sure if they intend to sue anybody, it feels more like they wanted to guarantee themselves getting the patent by threatening anybody who might get the same idea. Besides, Yamaguchi (supposedly) admitted to simply cloning the dock without building in any other distinguishing features. Also, who's to say that the authors of Rocketdock, Mobydock and RKLauncher didn't get similar letters?
Do you know of any launcher-panel-with-icons-that-zoom-when-your-mouse-gets-close thingummy that existed before Apple's?
For the record, I think software patents are ridiculous and stupid, but within the confines of currently existing rules they received it legitimately.