My husband actually called them today and they had rooms available! They must have released a block, as we had just phoned and e-mailed them last week and they said they were still booked. So much for the wait list! Thank you for posting that you made reservations there!
I could have written your post about the "cons" for SoG myself! The bus issue is a big one for me, too since they require the child be out of the stroller and the stroller folded. Like your nanny, I'm sure my mom could do it just fine, but the monorails are definitely easier!
One consideration about the cab (when you mentioned this I started thinking about whether that would work for my mom), is although we'll have DD's car seat, putting that in and out of the cab would probably be a larger hastle than the bus/stroller thing. I don't know if that's a consideration for you...
I would also like to (possibly) do the
disney dining plan, and have my mom use magical express...both of which aren't available at SoG. On the plus side, shades of green sounds like it provides a nice spot to watch the runners from before going to Epcot, and is close to the monorail. So, we've got some logistical things to work out as well.
Have you stayed at POP before? In April we were planning to do half at Yacht and half at Pop, but were really turned off on Pop at check-in (never saw a room, though), and switched to AKL. Because of the great pricing, and figuring there might be a different crowd there with the marathon, we were thinking aobut staying there. Any opinions are welcomed!
If you think of any other pros and cons please let me know. We're just glad to have a room within walking distance of the monorail for less than 250 per room per night!

Now I've got to add in the value of the meal plans, parking, and magical express to see if it'd be a better deal to stay at pop most nights, and have my mom (and DD) stay at Poly just the night before the half.