Great topic! Assuming I'm home when TSHTF, like you I'd be stongly inclined to shelter-in-place unless the event involves something that directly threatens me. But I think my reasons are different from those of most folks on the ETS forums. For one thing, with about 2 million other folks in Manhattan proper and only a few bridges/tunnels leading off the island, the lines to bug out would be just horrific -- I'd need an awfully good reason to leave, which means:

• As to natural disasters, I'm on the 23d floor, so flooding isn't really an issue ... if there's a quake I'd stay home for a couple of days (if the structural integrity hasn't been compromised) until the crowds clear out, then head for friends or relatives with homes a little closer to the ground ... my building is supposedly fireproof construction, so structure fire is pretty irrelevant (though the resulting smoke might be a problem) ... and hurricanes, well the bathroom is windowless so no danger from flying glass, and I guess I'll just have to hope that the building was built to code.
• As for terrorism, if it's a field-effect attack (dirty bomb, aerial distribution of smallpox, etc.) I'd have a tough decision between bugging out and just sealing the h--- out of my windows & doors with duct tape & plastic sheeting ... if it's a localized attack (like the WTC or last week's London bombs), I'll bug in unless the attack directly affects me or my apartment.
• In case of civil unrest, well I figure my building's super would arrange for security on the ground floor and/or shut down the elevator (and I figure most looters wouldn't be climbing 22 floors to get to my apartment).

On the other hand, if I'm stuck at the office out in the 'burbs (as happened with both 9/11 and the August '03 blackout), I'd be somewhat more inclined to consider bugging out ... I have a minimal BOB stashed under my desk, including hiking-friendly footwear, and colleagues who have generously offered me shelter when I was stranded those 2 times, so I'd have lots of choices.