This is fascinating. Researchers have been looking into skyscraper emergency situations (per this paywalled Newsday article) and have calculated the biggest delays for those escaping the WTC on 9/11:
1. Gathering personal items: 40%
2. Seeking out friend/co-worker: 33%
3. Searching for others: 26%
4. Phone calls: 18%
5. Shutting down computer: 8%
6. Waiting for direction: 7%
7. Gathering safety equipment: 5%
8. Changed shoes: 3%
9. Seeking permission to leave: 1%
Those same researchers also seem to think elevators might actually be pretty good during an emergency (because of stair blockage). So there you go.
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