In the sprint events they all (nearly all?) use a six-beat kick. In the backstroke Ryosuke Irie uses a kick that looks like a two-beat with extra miniature kicks. In the 1500 most of the men use a combination of four-beat for most of the race and six-beat for the final sprint. Usually, in the 800, there will be some women who use a two-beat. I believe Becky Adlington uses a six-beat throughout and I think Katie Ledecky does, too, but will have to wait until video footage becomes available to be sure. Pellegrini is basically a two-beat kicker in distance races but I think she uses a six-beat for the 200.
Video footage of the London Olympics has not yet appeared on youtube as far as I know and may well not appear if the copyright holder has other plans for the footage.