Hey HN,
Got tired of waiting for Apple to add this feature, so I decided to try to implement it myself. This is my first attempt at Cocoa hacking, so please feel free to give me suggestions if I did something wonky. Also, the plugin is open-source, so please feel free to check it out for yourself.
Thanks so much! Not having this feature made me feel very insecure whenever using Safari instead of Firefox.
Also, a tangential thanks for letting me know that SIMBL had been updated for Snow Leopard. The transition to Safari on Snow Leopard was difficult because all of a sudden all of my plugins no longer worked--no ad blocking, no auto-restore from last session, no force new windows to open into new tabs, etc. Brutal. Now I can go look for 64-bit updates!
Sweet! I had given up on this ever appearing -- Seems that since someone came up with it before apple the fanbois have a hard time accepting that it may be a good usability feature. (top 2 responses: "But history already has that" and "I never accidentally close tabs", both of which ignore the part where i leave browsers open for weeks at a time because I'm too lazy to properly organize bookmarks)
I really doubt there are many fanboys that really hate this idea, after all there's "reopen last closed window" already in Safari, the only reason against tabs is that it might work unexpectedly if you don't realize which window you last closed a tab in.
I've filed radars and talked to some Safari engineers about why this feature isn't in there and have been pretty much stonewalled, except about Cmd+Z to undo accidentally closing a tab that used to be in Safari (and is in the Glims 3rd party Safari addon). Not sure why it's still not in Safari, it's been years (literally)...