Amp Slide Cart Upsell Drawer

Both the app and support from the developer are fantastic. The app works seamlessly and offers both an Upsell module and a discount field that allows customers to add a discount code in the cart rather than the checkout. I previously used a separate app for the discount in cart functionality, which had quite an impact on site speed and which I've now been able to uninstall. I've never had such great support experience with any other app. The developer, Robert, is extremely helpful and implemented a number of customizations that I requested swiftly and expertly. He even fixed a coding error on our site.
Couldn't recommend more.