Thanks for weighing in, Angie, and everyone else as well. I really appreciate ALL of your opinions. I am still undecided, but will think about it some more.
Sarah, your point about comfort is well taken. I don't think there is any obvious rubbing going on (the part of my heel that touches is covered by the footie, and I'd probably wear real socks the first couple of times to break them in anyway) but I definitely need to wear them around the house a bit to make sure, if I decide to keep them. If anything is going to cut into my foot, it's actually going to be the FRONT panel.
Pastrygirl, I did try pulling the strap tighter to see what would happen, but it just seemed to compress the front part too much and do nothing about the gap in back.
A couple of other things:
--I am a bit worried about the finish. Already there are a couple of creases, and it will get worse with wear. I can tell that the top of the instep (where there is extra room) is going to crease when I walk because my foot doesn't fill it. I am not sure how badly this finish will scuff. I don't mind a little RATE (in fact I like it) but some patent finishes tend to get black scuffs which I don't like. I am not sure how to tell if this will happen.
--I am also slightly worried about the strap stretching out, although I suppose I could punch an additional hole if this happens. It is partially elastic; knowing me, I will probably get lazy and put them on without unbuckling (as I do with all my other shoes, LOL), which might make the stretching a problem.