Details are out on the Canon S3is, which is due to become available in North America in May. Apparently it is already available in Europe.
Reading over the specs, it seems that the third generation of our beloved S-series is simply a "get an update out of the door" model. Let's take a look at the specs (which you can read in detail at Digital Photography Review):
12x zoom, etc -- no changes there. I would like to see wider wide angle over longer zoom lens.
6.0 Megapixel -- up from 5.0. Not significant, except for increased noise, perhaps.
Larger size 2.0” Vari-angle LCD -- 0.2" larger than the S2. Bigger is better, but this is still small compared to the 2.5" screens that are normal today.
30fps VGA movies with stereo sound -- don't really need stereo sound, and I suspect the stereo separation won't be much to write home about. Even the S1 had 30fps VGA movies.
Photo in Movie feature -- could be useful. I find the photo feature useful on my video camera.
DIGIC II, iSAPS and Flexizone AF/AE -- lots of acronyms. Question is, do they take subjectively better photos. I suspect not.
2.3 fps continuous shooting performance -- didn't we already have that with the S1?
20 shooting modes -- I NEVER USE SHOOTING MODES!!! If you can't take photos in P or C mode, then why are you using this camera?
My Colors photo effects -- that's what PaintShop Pro is for.
High ISO Auto -- a fix for a bug in the S1 (and S2?), where it would tend to keep the ISO low, rather than going up to 200 when necessary.
ISO 800 -- I like that.
Widescreen (16:9) recording -- ho-hum. My 7-year-old Epson PC800 digital camera had that. You'd think it was just thrown in for lengthening the features list, but I find it useful for landscapes, when there would otherwise be too much sky and too much ground. Mountain ranges, for eg.
dedicated ISO button allows for easy switching between ISO sensitivities -- available on the S1 through the custom shortcut button.
dedicated movie button means users do not need to switch modes to start recording -- one of the great puzzlers of the S1. It also has this button, but it only works after you put the camera into movie mode. Another bug fix, I guess.
60fps QVGA clips for sharp slow motion -- QVGA and sharp do not mix. QVGA is quarter VGA, 320x240 resolution, which we had on the G1. The slow motion aspect is interesting, however.
manually adjust focus -- another bug fix. Movie mode cannot focus well automatically at 10x-12x, so here's the fix: get the human to do it.
2816 x 1584 recording pixels ... 16:9 format – perfect for ... printing wide (10 x 20cm) photos -- sorry, but it's not perfect. 10x20cm paper is 16:8 format, so there's going to be an annoying border on two sides.
new, dedicated Print menu -- who prints from their camera? This just means yet another menu for the already-crowded menu system
handy Print/Share button allows one-touch printing and easy uploads to Windows or Mac systems -- yet another button on the camera. Windows and Mac systems already automatically transfer photos; why the button?
The camera is compatible with MMC/SD cards -- and the reason I won't be buying it, due to the huge investment in CompactFlash cards. But I do like the color of the S3.