Because we have long layovers in London and Boston (on the way back), we're trying something new: we bought a 30-day Admiral's Club membership from American Airlines. Already we approve. In San Diego, we got to wait for our flight in a soothing room with comfy chairs, drinking, snacking, and using the wifi (all free.) Here at Heathrow, the AA lounge is vast, with an impressive open bar, many food choices, wifi, showers, and more.
What I like best, however, are the lounge chairs, in which I hope to nap. Our flight to Uganda departs in 4.25 hours, but I'll be content camping out here for a long as possible.