STILL waiting for 7.8 on my Lumia 900.
Finally got my update! I had almost given up. I downloaded the seven-eighter updater and was about to flash the phone via that method. When I plugged the phone into the computer Zune launched, so I thought why not try to check for updates one last time. To my surprise, an update was finally available. I guess threatening the phone was all it took. lol
Just got mine updated through Zune last night. 5 rounds of automatic updates went through, but now have 7.8.