I have an S400 also and love it. I basically got it for the same reason as you - my Canon 10D is too large to tote everywhere. I carry the S400 with me everyday in my briefcase. And the picture quality is pretty impressive. Just for fun, I took a macro shot of flowers and printed it to 13x19" and it turned out just awesome. People's jaws drop when they see this pic and find out that it was taken with this camera the size of a deck of cards. I do, however, prefer the Neutral color setting to the Vivid. The Vivid seems like Velvia and then some.

I picked up this camera at Amazon w/512mb Viking for $329.00. The S410 and the S500 had just come out and Amazon ran a special on the S400. From what I see, the S410 only adds a print button on the back of the camera. Anyway, like Michael, I highly recommend this camera.