I have a 20Mbs DSL connection. The 11GB install took 2 hours. Then the first start of the software took about half an hour more (downloading various additional data I believe)
During later starts, it takes about 3 mins to get menu.
A free flight typically takes another 2 mins to launch. Then, if data are not cached, textures (cockpit, external view) take about 1 min to get fully sharp. Though far from optimal, I would say I can leave with it.