I've been on a journey of trying to improve my online privacy and security for the last few months, and took the step to buy a Pixel 6a recently with a desire to switch over from iOS. The installation process was incredibly smooth, and it was easy to get up and started installing my initial apps from f-droid and the aurora store. I really like the sane defaults which graphene provides. I've come across some issues which I think will be big blockers to me switching to graphene as my daily driver.

Navigation

I currently live in a European capital city with extensive public transport. Apple Maps is my daily navigation app, as it is very good at navigation for public transport and makes a good-faith attempt to be private in how it uses your location. I have tried to use Organic Maps and OsmAnd however they offer very poor support for public transport where I live. They're essentially unusable for my use case. I then decided to install Google Maps using sandboxed google services. I read through the guide on the graphene website on how to get this enabled and have managed to get navigation I would expect with good support for public transport. However, I'm quite concerned that to get this working, I need to enable Google Play Services to always have access to my location. I find that sometimes when I'm using other apps and not even using maps, google services will just start accessing my location momentarily, which I'm not comfortable with. I know that, as I'm not signed in, Google cannot associate my activity with a specific account, but it can still in some ways fingerprint me, phone home, and I'm not sure if there are any implications to allowing google services to access my location all the time. The location permissions needed for Apple Maps are not this creepy.

No Simple Backup solution

You can definitely argue that this is just me being a pampered apple user, but hear me out. iCloud's backups are useful for making sure that your data isn't lost. I know that some parts of iCloud are not E2E encrypted, but apple is attempting to rectify this with the incoming advanced data protection. I think it would be useful if Graphene had some sort of optional hosted backup solution which made this transition easier for people who for example are used to google drive/iCloud backups and are not eager to handle their own backups. Some people also just aren't very technical/don't have the time, so not having an easy backup solution does mean I need to invest more time into sorting something out for that.

Other small things which are more android specific and not graphene

It's nice that on iOS there are some UI/UX design guidelines that most apps follow, and it makes the experience across apps, so it makes the experience smooth. Maybe it's just me, but I feel like the UI of a lot of these FOSS apps on android don't look good at all. It's quite a jarring experience using some of these. Even for the default apps installed in graphene, the design is not uniform across them and I feel like I need to install alternatives because I feel like apps looking appealing and consistent is an important part of the experience. Apple has a consistent UI experience for their default apps, and so I never see much need to install alternatives.
Visual Voicemail doesn't seem to work for my carrier. I decided to just disable this, as I get texts when someone leaves me voicemails.
I will never understand why android emojis look the way they do. I put this at the bottom as it's petty and not relevant to graphene, just relevant in my switch from iOS.