In the Northern Hemisphere, Shavu'ot falls in the late Spring or early Summer. As a result, sunrise is relatively early, so learning "all night" and then praying the morning service at the earliest optimal time would mean timing the service based on a sunrise of, e.g. 05:36 in Jerusalem in 2012.
By contrast, in the Southern Hemisphere, this holiday falls in the late Autumn or early Winter, so the night is longer, and sunrise is significantly later: 06:48 in Sydney in 2012 and 07:40 in Capetown in 2012. As a result, people there who learn "all night" have to stay up an hour or two more into the morning than those in the North.
I'm wondering whether, as a result of this difference, the practice of learning all night is either less prevalent in the Southern Hemisphere, or perhaps whether alternative schedules (such as this one) are more prevalent there.