Even with the Central Line being closed it was fine yesterday evening. We were out of our seats and on a Jubilee Line train in about 35-40 minutes last night. Also last night it was an 'everyone out' scenario as nobody could stay in the Olympic Park or the stadium. Come the games, there will be a bit more of a steady, heavy flow of people rather than the whole lot emptying at once.
That's not to say that there won't be serious transport problems during the games, but the negativity isn't always merited.