So, they don't have any known crashing bugs, and until now haven't seen much need to actually write a Mac-optimized version of Flash Player. Except now they're rewriting Flash's graphics engine, going from a direct port of the Windows version to new Mac-optimized code that makes use of Apple's Core Animation framework.
While a lot of the attention has focused so far on iPhone/iPad, this is the part really worth watching: Adobe knows Flash is a performance hog on Macs, and Macs are now finally a big enough (consumer) deal for them to address it.
Bonus nerdery: Flash engineer Tinic Uro discusses the technical details about why Core Animation and Flash should be like peas in a pod.