It goes without saying that you should let it install all the updates that are available. Early on I had some lockups etc. but the frequency of that has dropped right away.
Me too. A Bluetooth keyboard works fine but I was not able to get Bluetooth (music) sound output to work (so far).
I think GPS (GNSS) is not working in software yet.
It’s working for most people. I don’t think that it will automatically mount. Start with
ls -l /dev/sd*
What type of file system (e.g. ext4, vfat, …) and what capacity of card (e.g. 32 GB)?