The speed and low latency is fast enough to stream multiple HD movies at once and still have bandwidth to spare. It also can play any online game.
Latency tests during the beta phase are in the 20-94 millisecond range.
SpaceX is testing laser communication between orbiting Starlink satellites. Laser communication will greatly speed Starlink communications and further reduce latency and increase download speeds.
SpaceX reports over 700,000 potential customers have pre-signed for Starlink service.