think all who bought the obscenely expensive AP sets just less than a month ago are now super butt-hurt now.
but that's life if u wanna be early adopter.

well below is my personal feedback for both devices..i'm not able to test everything yet, so i'll add it from time to time..

web browsing:
tested with DiGi sim card, sensation has better signal and bcoz of that, it manages to load the website faster than sgs2..
on wifi, still Sensation loads faster, no matter simple html site or flash site..
in terms of website smoothness, both are on par.. not as smooth as iPhone 4, but still at good smoothness level and definitely better than incredible S..

personally, i prefer Sensation for web browsing.
video camera:
- Low light: sgs2 has cleaner picture, but i think the noise reduction is too high cause the picture to lost lots of details. while Sensation shoots sharper video, with lots of details but has more noise.

- Day / under sunlight: i can say both is on par and moving objects look smooth, although personally i feel sensation fps is more constant than sensation.

- sensation offers touch to focus features during video recording..

camera:
- sensation snaps pic quicker but u need steady hands to avoid blurry pics
- sgs2 is a bit slow too focus but the pic is slightly nicer under low light condition. again samsung tends to over do the noise reduction..

personally for video i choose SGS2 while for still image i choose Sensation.