I'm still waiting for the update here! No notification on my phone (I've set it to notify when updates are available) connected to zune also to no avail. I did the so-called trick method also and nothing happened. Waiting very patiently at the moment lol
Can't wait to reorganise my start screen la!!

Ok downloading the update at the moment using the Zune trick! Turns out you need to leave your phone in airplane mode for it to work. I forgot!

Sorry late reply! Have you got the update yet?
If you havent do the following steps:

1. Put your phone into airplane mode
2. Connect to your PC and start Zune, open your network connections too and run it beside Zune.
3. Click on "Update" under settings and give it a few seconds (mine was 10secs) then IMMEDIATELY DISABLE YOUR NETWORK!
4. If you've timed it properly, Zune should show that an update is available for your phone and then you turn the network on again and DOWNLOAD!!
5. Should it not work, enable the network, click any tab besides "Update" and then click "Update" again. Then repeat step 3.
For me I didn't get 7.8 straightaway, I had to download 2 other updates before that. Something called the "Tango Refresh" and something else I forgot the OS Number sorry. But yeah anyway you do get 7.8 in the end!!

Good luck mate! Wish you all the best haha. If there is any problem or my steps weren't clear enough, just hit that reply button lol.