I don't think regulated 18650 cells is a problem, but most users don't know the difference. With every other laptop, you can pop out a battery and replace it with a model with the same part number, but with 18650 cells that's a lot harder to accomplish. I'd rather see them "package" a bunch of 18650 cells together with its own part number and lets the people who know how batteries work figure out how to add their own cells (anyone with background knowledge will recognise the pack configuration the moment they take out the screws!)

I don't know about M4, but with the M3 Apple's compute-per-watt was already behind some AMD and Intel chips (if you buy hardware from the same business segment, no budget i3 is beating a Macbook any time soon). The problem with AMD and Intel is that they deliver better performance, at the cost of a higher minimum power draw. Apple's chips can go down to something ridiculous like 1W power consumption, while the competition is at a multiple of that unless you put the chips to sleep. When it comes to amd64 software, their chips are fast enough for most use cases, but they're nowhere close to native.

A lot of Windows programs run on .NET, which is architecture independent, especially if they target UWP (which is more common than you might realise). The remaining applications will need porting to get decent performance, but the most important applications (browsers and Office) already work.

Re: Windows: Windows on ARM already has a binary translator, developed in part by Qualcom, that comes pretty close to Apple's Rosetta2 for many types of software. It's not as complete as qemu-static is, though it is faster for the software it does support. The worst part of the translation layer is that the ARM chips made by Apple's competitors just aren't very fast in comparison.

I believe Steam can distribute different binaries (there were games with x86 and amd64 binaries for a while!), but until ARM laptops with decent GPUs start coming along, I don't expect any game devs to use features like that. Still, apparently current ARM devices can hit 50-60fps with current gen devices already, and the upcoming Snapdragon chips are supposed to compete with Apple's CPU, so who knows!

Microsoft already tried (and failed) to make Windows on ARM a thing before with the Surface RT. I hope they don't go all Windows 8 over their current attempt...