Yep, that’s right, the heel is wide and comfortable and provides plenty of support. My wife’s able not just stand on it, but even catch a bike if it’s going to the side without any problems (well, until it’s gone far enough, of course).
Regarding the shifting – it’s not a problem for her now at all, though it took some time just to get used to the feeling. But you’d have to spent some time getting used to the new shoes anyway, I’ve been changing from Raytek Xenon to JR Streetburners to Sidi Vortice myself and had to spent a couple of rides breaking each of new shoes and getting used to shifting/stopping in them.
One thing about the Icon boots you have to keep in mind, though – they’re quite narrow in the ankle, so if you have wide feet it will take a while for you to break these boots in and start feeling comfortable. And they’ll restrict your movements during this time quite a lot, though after that the boots are just fine. To speed up the process you may just wear them around for some time, before getting on the bike, they’re comfortable as a general-purpose walk-around boots as well.