Build seems solid from what I can tell. Managed to migrate (from lede-17.01.4) mostly painlessly. Did run into two issues:
Running the 18.06.1 sysupgrade in 17.01.4 led to a brick. A strange type of brick where the router was already waiting for a TFTP recovery without my intervention. Flashing the factory.img at this point worked fine. This was with and without "keep settings" checked. It was not even booting.
mdadm does not work with raid1 correctly. To be fair, it didn't work at all in 17.01.4, but it does with a workaround on 18.06.1. But the default /etc/init.d/mdadm has it use the /etc/config/mdadm and all that jazz, but when it runs mdadm --assemble --scan, it segfaults. This can be reproduced on the command line. My workaround was to hard code my drive paths into the init.d and skip the scan process. It then works as expected. LVM is still broken (with raid1).
Otherwise, I have not ran into any issues yet. 5ghz seems stable so far, but its only been about 5 hours uptime. I remember falling back to 17.04.4 stable because snapshot had 5ghz instability.