anti shake only works as well as the person using it knows its limitations...
digital types, like what Casio calls its DSP (digital singal processing) anti shake only works to a limited extent as it uses software to try to correct the image after it has registered on the imaging chip...in other words, it trys to "unshake" an image with shake, correcting after the act of capture...a bit like what Photoshop CS2's smart sharpen can do...
optical types, that move a lens element or sensor, like those from Canon, Nikon, KM, Panasonic, etc. prevent the image being captured from having shake in the first place...in other words, the image registering on the chip should have the "shake" corrected by the mechanisms, correcting before the act of capture...
as you can guess, not capturing the shake works better than trying to digitally correct the shake...how well it works depends on each company's system and that is always going to be a point of debate so no point going into that discussion here...of course, if there is a camera that uses both types even better...:think:
as for low light, well, it's not so much low light being the problem but slow shutter speed...and it depends on how the antishake system...if its an "always on" system that takes into account slow (long period) shake, then it might work better...and of course, at long focal lenghts, any shake is magnified...I have shot a pretty steady low light shot, 200mm (300mm at 35mm equivalent) at 1/6s handheld at iso3200 so I know it should work in low light...