I've had a disagreement with a friend over the use of 'on' concerning the the launch of a certain product. He insists it should be 'at launch' while I believe either 'on launch' or 'at launch' is fine. I would greatly appreciate any light shed on this quandary.
While "at launch" may be more common, I do believe it should be "on launch" simply because the launch time is just that: a time. If we were to include the place I'd be more inclined to agree with your friend (such as At [Sydney's] launching).
The game launched at Sydney on Monday.
The game launched on Monday at Sydney.
On the game's launch at Sydney.
On launch, the game blah blahed.
At the very least you could use either.
If it is being used for the launch of a product, "at launch" seems (after some very basic research...) to be more usual, with a meaning of "at [the time of] launch", as in these examples:
"On launch" seems to be used with a sense of "on starting", describing an action or event rather than a time:
Of course, this leaves a very large grey area.