I would go with the SD400, which is also from the elph family. I have been using the s100 when it first came out in 1999 and have loved it. The SD400 takes SD cards and are half the depth of the S100. I'm also thinking of getting it, but might stick with the SD300 (4 mpx).
Tofi, yup I like the sleek and slim SD400 as well, but I read a few reviews online where people said the LCD screen developed crack after a few days/months w/o the camera being mishandled?
only thing going for the SD-500 is the sleek design and weight.. except for that feminine appeal it can't touch the 610..
The A610 is possibly one of the best P&S available on the market today for that price.. oh and i didn't get that "available to me" prices... brand new 'dubba band' from reputable authorized dealers online, A610 is $263 and SD-400 is $289 !!
the A610 has over SD-400
larger (better) sensor
zoom range .. (35-140mm vs 35-105mm)
allows manual focusing
better macro mode (down to 1cm vs 3cm)
more WB options
better lens (f/4.1 at tele vs f/4.9)
faster top shutter 1/2500 vs 1/15000
more powerful flash (14 feet vs 12 feet) + allows external flash
full control over metering .. Av, Tv
external screw on lens options available
faster drive .. 2.4fps vs 2.1
flip out & twist LCD
uses AA rechargeables..
costs less!!