The old shop is an essential thing which should be returned.
The new upgrade is cool. I only hate the fact that I can't see how much I am adding, but I learned to compensate by doing mental calculations. Holding down a button to see details is troublesome, though. And did I ever mention the fact that I don't like the way our items are organized? I want the same things grouped together, thank you very much.
So, I vote return the old shop, and minor to major tweaks for the new upgrade.