People reason that if a skill is important, people need to become good at it, and becoming good requires starting early in life. This reasoning isn't valid for computer use, and I have an anecdote to illustrate why.

When the internet was yet fairly new, I was assigned to teach basic computer use to a class of Saudi Arabian soldiers. Many of these guys were fresh out of the desert, some even still adjusting to the idea of wearing shoes. They had no idea what to do when placed in front of a computer. Imagine if your dog got up on its hind legs, rested its paws on the keyboard, and poked its nose at the screen. To cut the story short, I led them through this and that and by the end of a month, they certainly couldn't touch-type, but they were designing their own web pages. They were so enthusiastic that they were sneaking into the lab after hours (evidently to search online for pics of naked ladies).

My point is that computer interfaces are designed to be simple and intuitive, so you don't need an early start to practice like you do with a highly complex task like playing a musical instrument. There is really no developmental benefit to early screen use.