The S90 shutter lag is .44sec in full auto focus and only .088 in pre-focus mode.
A 24mm lens like the LX5 behind a flat port is hardly wide and shows considerable edge distortion and even color fringing. As well, the S90/S95 can utilize a wide variety of accessory lenses depending upon housing chosen, the LX, not so much.
I find the Canon S90 quite fast and responsive. If you need faster response then go to manual focus and zone focus with the fisheye lenses. They have so much depth of field perfect focus for a given distance is not required. of course, a dSLR is faster but really, I have not found this to be much of an issue with this particular camera.