Re: Downside???
Um. The internet? Or specifically, it allows us to continue to bring the internet as it grows without losing performance and functionality. Surely that's something people want?
Also, v6 addresses aren't necessarily hard to remember. For example, here's a URL for accessing a site over v4: https://www.sprint.net/, and here's the v6 equivalent: https://www.sprint.net/. It's hardly more difficult to remember the second than it is to remember the first.