I wrote an e-commerce store in rails just under a year ago. I did some of the same research, and I looked into Spree & Piggyback. Spree has a talented team and I was excited to try them but I found the project buggy, huge code base, & very inflexible.
In the end, I decided to roll my own solution from scratch and use Stripe instead of using one of the pre-built solutions. In hindsight, rolling my own solution was the way to go and the time spent starting from scratch was probably quicker than having to learn something like spree anyway.
