I have had quite good success with this. Make sure your computer clock is set correctly.

Navigate to the page to request the upgrade, and just keep refreshing it or switch tabs,(you don't want your log-in to 'time out') until your computer clock ticks over at the 96 hr point, request your upgrade then. It takes a few minute to go thru and think etc, and then voila....!

With R2 you have a fair chance, especially if it is R2 after the 7 day window has passed. It also depends on when the flight is, (day of the week) and what flight segment it is, this determines how many other E's are in Y waiting for that upgrade?

For 2011 I got 9/10 upgrades I requested, and one on UA that I did not even ask for!!!