Terzi Caffè
They had a "beans menu" on display and you can choose which beans you want for your espresso. The barista uses proper weights to ensure it's the best espresso you've had in your life, and the ceremony is completed by having your coffee while standing in the bar, like the locals!
It was so busy you can't really aspire to get a seat in the rear anyway (let alone work from here with your laptop). Best to drink your espresso and get going!
Quite picturesque place as well. Be sure to have a look around before leaving.