After that? I only had one application fail due to Graphene's memory allocator. No weird bugs, no need to restart like some siblings are commenting. As close to the "Graphene just works" as it could be.
However, I'm not heavy into Google's ecosystem. Google Pay will not work but I'm not a user, some Google features won't tell you why they don't work but I'm not using them either (Quick Share for instance), none of my apps require the highest Play Integrity level. Maybe the person who say this are a specific type of person where use-cases don't overlap with what breaks on Graphene.
Firefox + stock keyboard stopped properly working three days ago, it's back to normal now. No idea what that was about. Restarting was the only way I found to get things working again during that period.
While on the stock Android keyboard, it is clear that the Google one is much better at correcting my taps than the stock one. My typo count has gone up significantly.
Every several weeks the mobile connectivity stops working and nothing short of a restart will get it working again. This might be a bad interaction of the very weird way Google Fi works with a secondary user account.
I've encountered one case of the phone shutting itself off to install an update overnight and not turning on, making me miss my morning alarm.
In the US, there's no way to side step the lack of tap to pay.
Getting apps to work with Android Auto requires some finessing.
These are the things I've encountered in the last 2 months of using Graphene.
Aside from all of that, I really like everything else about the OS. As it stands, it does lacks polish when straying outside of the common path. Not using a secondary account, nor Google Fi on an eSIM, and using the stock browser would likely improve my experience significantly.
I haven't encountered an app that wouldn't work yet (but have installed play services as I do want to use Android Auto).
I would still recommend Grapheme for normal-ish users, as long as you don't go "paranoid mode" with secondary accounts and skipping play services or don't want to use the phone for tons of things beyond phone calls and web browsing. The base experience is that much calmer than stock Android on Pixel.
I don't use RCS and Android Auto.
I have HeliBoard to replace Stock/Google Keyboard. It is way ahead the stock keyboard experience but far behind Google Keyboard's, especially when writing in two languages.
Tap-to-pay works with my bank apps. But that means I can only use one card unlike with GPay.
I rarely use second account as the latency to switch from one account to the other is a pain. I only have a secondary sending notifications to the first one.
I don't let the phone auto-reboot for installs, I let it install automatically and click reboot when I want it to install.
I am on a physical SIM / different carrier and never encountered network issues so I can't comment on that one.
(idle interest; I use Graphene, but few apps, and everything worked so far)