Since upgrading to Safari 6.0.4 I have had repeated computer crashes. I noticed a discussion at Apple support
Implicating SIMBL, which Safari Cookies apparently uses, in repeated Safari crashes. Nobody else reported the whole system hanging, which is what happened in my case.
Also my computer (running OSX 1.8.3) has a Crash log saved with a filename SIMBL.
If there is a compatibility issue here, it is quite serious. But it does not show up all the time. I cannot say what triggers it.
If SIMBL and Safari Cookies are to involved in my crashes, I hope that the issue can be resolved as I like what this useful add-in does. And speaking for myself only, I hope it is not my Macbook Pro hardware that is to blame.