Let me add...i have the same issues...
820l about 5 feet high in the center of my apartment. Small place...my gf has an apple tv, and I have an ouya in the bedroom about 30 feet max from the router. Both units are inches from the door, and the doors fake wood lol but the signal drops. One day its great, next its impossible. Everything wired to the router is ok. My mac mini is wireless and about 4 feet away. Feels slow, but speed tests are solid.
broadcasting both bands, for older and newer devices. Wpa2
I've had a Lumia 900 and 1520 with no issues. An old kindle no issues, but my gfs iPhone 3g, 4, and 4s drop.
sorry for the rant...im ready to change routers, again. Lol