Yah, personally I am looking for a second camera that will fit in my shirt pocket for motorcycle touring. My A620 is just too big. I assume the A720 is about the same size as my 620? So, I am deciding between the sd850 and sd870. I think they really ought to be the same price, but oh well.
For a slightly larger camera, I would lean towards an A650 over the 720. If you haven't noticed I admit I am quite partial to Canon and also to OIS.
I have to agree with corkyg the S5 looks super nice too.
I have to keep it to two camera's and one has to be pocket version, and one needs to be wife friendly. I have to admit there have been a few time I sure would have liked an ultra-zoom, but not too often.