Every time I see the lift just set off as I arrive and decide to tactically take the escalator; I regret it. There is nothing worse than seeing people run from the lift, whilst you're another 45 seconds from the bottom of the tortoise of an escalator.

I don't think I've ever waited more than 2 minutes for the shuttle, so unless you are unfortunate enough to see it set off as you arrive, waiting would still probably be faster than the walk, albeit less predictable and more sociable.