I don't let Tesla update any cars anymore, except the Model 3s... which I just haven't taken the time to bother with as of yet.
My primary S is still running 8.0 BETA... yeah, that's build date: Tue Sep 13 19:01:51 PDT 2016
As far as I'm concerned, there has been no net improvement since that point from a user perspective to pre-AP2 vehicles. There have been some improvements to maps (which is probably what will get me to update eventually)... and that's pretty much it, IMO. The UI has been downhill since then for sure. The improved browser, AFAIK, isn't available on MCU1. AP1 has not been updated at all since that time (except for changes to the CPU side code to tighten hands-on-wheel stuff, no changes to the NN so no actual improvements).
Tesla can and does force updates, and they do it in a way that looks the same in the logs as if you scheduled it yourself. I've seen it done to at least a half-dozen cars. Not really sure the reasoning, but they definitely do it. The can also force it from garage easily, which is how they do it on Tesla-owned cars to auto update them, but I've not seen that method used on a customer car.
It's annoying, overall. I don't consider Atari games, farts, etc to be improvements to the car at all. Loss of dual windows is a huge loss of a good feature from v8 to v9. Overall, I don't really like v9. Honestly, I prefer the v7.x UI where nearly everything important is one-touch away. Now in v9 everything is stashed behind a bunch more touches and delays (waiting for menus to popup and such).
I think eventually, especially with pre-AP2 cars, we're going to need to just start an OSS project to replace the Tesla UI.