I bought this case along with the Ixus 400, to protect my new investment. So obviously any comments about the size and compactness of the case are relevant solely to that camera.
Pros, the case is not bulky and has a loop on the back for going around a belt. It's (as another reviewer said) collapsible and branded, with a reasonably sturdy Velcro fastener. There's also a hole to feed a chain or strap through, which is a nice touch. Other than this hole (and the main flap) there are no other openings into the case, so it's certainly splash-proof. It's also well put together, and shows no signs of loose stitching or badly matched panels.
Cons, the case can be a little too snug - if you try to remove the camera by gripping the edges, it's easy to open the battery compartment rather than take the camera as a whole out. There is no room or pocket on the case I received, which is different to that reported by at least one other reviewer. As the collapsible sides of the case currently bend inwards it's possible to catch the various dials and buttons on the camera when putting it into or removing it from the case. I would hope that with use the sides will straighten and this will no longer be a problem. The case is not padded, so it's only reasonable purpose is to protect from scratches and dust. Don't look to this to provide much in the way of shock protection.
Overall, it's nice to have, but I'm a little disappointed that such a case wasn't included with the camera itself.