I'm running High Sierra DP9 on my Mac with Xcode 9b6. I've been creating builds of my iOS 11 app without trouble and submitting to TestFlight for internal testing.
This machine was using HFS+ up until yesterday. Since converting the boot volume to APFS, the archive still succeeds but is missing several of the critical app icons which means TestFlight rejects the app on upload.
Looking at the build log, actool (the thing that takes icons from an asset catalog and puts them in the right place) is for some reason ignoring most (but not all) of my icons.
I filed a bug with a ton of documentation (34227266) but before I roll back to HFS+, thought I'd put this out here in case anyone else has seen this problem. Also interseted to hear from people on APFS and building without any trouble.