RetroPie

If you are looking to run RetroPie on a Pi 3 B+, and currently have RetroPie running on a Pi 3 B, consider upgrading your installation.  I followed the guide linked here without issue.  I performed the upgrade while running on the Pi 3 B.  Once finished, I moved the SD card over to the new Pi 3 B+ and booted.

https://retropie.org.uk/forum/topic/16145/retropie-upgrading-raspbian-jessie-to-stretch

Some Tips:

• As a precaution, I disabled all overclocking I had set in the config.txt file prior to upgrading.
• I thought Step 2 would be involved; however, there were only 6 lines of code to read through and 4 instances of the word “jessie” to replace with “stretch”.
• There were a few times during Step 4 that a prompt appeared requesting permission to keep or overwrite a file.  The default was “N”, so I chose the default.
• I skipped the Optional Firmware Update…for now.  The comment regarding “reverting back to a stable version…” implied the new firmware would be unstable.
• In Step 6, I used the binaries and installed (almost) everything.  I ignored experimental features and drivers.  Having only the Xbox driver installed, I updated that one via the source, as opposed to installing drivers I won’t need.
• I use wired controllers, so have not tested Bluetooth ones.  Some additional steps may be required.