Hi

I've used studiocart on only one website so far, which will go live soon. Product is promising. Support is great. I remember them sending me a code snippet for a small feature that wasn't there yet!
Some features are still missing such as upgrade/downgrade memberships but I trust the team. they'll bring it. And I'm sure they'll also bring more integrations with other appsumo products so grab at least 2 codes if you do client works!