Just FYI, I did some 5Ghz testing yesterday, same room 8-10 feet using my DWA-180 adapter. Initial speeds were ok, however i got a momentary disconnection message in Windows. I canceled the file xfer and re-started again, Speeds increased by 4-5MB. Not sure why speeds were not as fast when I first started. I believe something to do with Bursting had not kicked in then all of a sudden it did. Speeds were Low to mid 20MB's Write and Mid to High 20MBs for Read. I was testing isolated from internet and using a wired LAN Gb connected PC with folder shares.
I saw no other WiFi drops or disconnects after this. I'm thinking of doing some duration testing and watching a movie with a bridge attached to see what I find there. New FW seems pretty good here.