Did they finally update the pen to something better? Seems like Lenovo's been using the same old cheap AES pen for the past 10 years.

Indeed. The essentially unreplaceable battery is one of the two major reasons why I have never bought a Surface (or similar unrepairable device) thus far. (Display reflectance is the other.)

These machines are amazing until some problems arises.
Even some stupid thing like changing the battery is something that makes you regret not having purchased a maybe less fashioned but more standard laptop.

In my company we have about ten Microsoft Surfaces 4 Pro, really amazing machines, I really love mine when it comes about speed, lightweight and portability.

But recently, since I've worked some years in the past as pc/cell phones technician, my boss asked me the favor to replace the battery in one of them.

Because of course, after some years of standard (merciless) office use, constantly plugged and unplugged to the charger without any regard for normal battery live preservation measures it had swollen up like a balloon, deformimg the back case and the display.

Well, I managed to replace it, but to do that you have to unglue the display panel (wich is like soldered to the back case with some kind of alien bomb-proof adhesive), hoping that the display itself won't crack in million pieces while pulling it out.
And the chances of cracking it are like 90%, like in my case, so I had to manage finding also a new display panel at a decent human price.

After that you'll have to remove some metal connectors shields, disconnect the flat cables, remove the heatsink and fan, and try to gently keep lifted the mainboard while removing the battery and its connector, both glued to the back case with the same alien bomb proof adhesive.

Once you managed that, you have to remove all the old alien bomb proof adhesive, put some new one (you'll never find the same, it's something not from this planet) and close it all back after a good test session.
I really don't want to imagine closing it and find out that wifi or touch panel or some other stuff isn't working.

So in the end a simple operation like changing a battery took me two weeks of pain and curses (meanwhile I had also my regular work to do, wich is not that, a family and a private life, so not 100% committed to this like also my boss said), a new battery and a new display panel.

So thank you Microsoft for not using screws and hook, so ugly and out of fashion.

As I said, I love my Surface, excellent machine until all goes well.
But the amount of pain and cursing in the event of even small and idiotic problems is absolutely not worth it.
IMHO