The new app store looks fine inverted IMO. I don't have any issues with lag. Auto updates can be turned on or off for all apps or individually. Entirely up to you.
And the Play Store has already auto updated itself to 4.0.26. It squashed a couple minor bugs. And I believe button resizing (larger "update" and "install"/"uninstall") buttons are on the list, along with making the icons in the store smaller, in order to use more real estate effectively. Here is the Play Store inverted: