This article was quite an interesting read
http://www.gamesindustry.biz/articles/digitalfoundry-tech-focus-battle-against-latency
From what I can see, the DS3 when running on a 60FPS video like the XMB has 50ms between input and display. That was measured on a CRT so there is no additional lag added.
That's not controller latency specifically, as it is also how long it takes the PS3 to get that input, render the change and output it to the screen.
From what Mark said at the press conference the changes they had made were to the controller itself, though that could be me reading too much into his words.