Apple has a monopoly on their hardware, and they will likely sell a significant number of devices. This will lead to a lot more development for ARM that never would have happened otherwise.
That, in turn, may make tilt the balance in favor of ARM for a lot of other use cases outside of OSX when other tools, applications, and hardware vendors better support ARM.
As for switching... I'm increasingly unhappy with Microsoft's complete disregard of user privacy. Apple isn't perfect with that either, but IMO much better at least. For my use cases, Win and Mac are the only credible options due to software availability. So to get away from Windows.. there's not much choice these days.
What makes ARM so exciting? Maybe battery use will be better? Maybe it will be slightly faster? Maybe? There's also been a lot of tuning done for laptop workloads on x86, it's definitely a maybe. I expect the only noticeable changes for most users to be somewhat better battery life, some apps not working, and occasionally having to know which package to download.