At least I can tell you the 3 soft buttons are more responsive than the ones on xs. And flaps on the phone because its water-resistant, unlike xs. It comes with version 4.0 onboard, basically a clean installation of ICS which means less issues compared to phones upgrading to 4.0. Not to mention the material feels better than that of xs, IMO.
I believe smartphones that are recently released with ICS out-of-the-box are highly optimized for the OS.. so, for those that are released with GB, don't expect better performance/battery-life if the upgrade comes subsequently.
Of course, it's a different story if the upgrade is through rooting..
BTW, loved the stand/charging cradle that comes with the Acro S package (I think this is not included for Xperia S). Courtesy of the side charging contact points on the phone and good design of the cradle, charging the phone is now so convenient and graceful. The USB input on the cradle works with iPhone power adaptor but not with the computer.
Photo image quality seemed good but speed of auto-focus+capture though fast, is still noticeably slower than HTC OneX. The camera options available is mind-boggling.. very similar to those found in my HXV9.
Battery life is average.. after some downloading (~50MB), Surfing and music playing for around 2hrs, it dropped to 75% charge.