I tried and tried to get the zune trick to work on my flash, never could get it work. AT&T Branded and locked (thanks tango)
So I had to resort to using the SevenEighter Tool to update with. 7.8 tool will make a full backup of your phone before it install any update's...So in case you do run into problem's you can restore it back to Mango/Tango in Zune..
If you phone is up to date already with Tango, then you will only have 3 updates to go through with 7.8 tool..
Just remember to select all the languages in the 7.8 tool for each update..
I have not noticed any problems what so ever, camera is working fine including the buttons. No error's with marketplace and all my apps are working fine did not have reinstall anything at all..