Hmmmmm....this is going to be a tough choice. I enjoyed the swords and soldiers demo. I've heard good things about hoard and costume quest. Already own peggle and shatter.
My free shipping experience with amazon has been all over the place. The quickest I've ever received a game is 3-4 days after release date. On average for me it's been about a week. The worst has been 2 weeks after release date, but that's only happened once.
I was in the same dilemma because my prime expired so I couldn't reorder and apply my credit. I emailed amazon and asked them if they could apply it to my dot heroes preorder and it was done within an hour.