Eventually, when my Gaggia is working again, I'll try this lovely "South Italian Blend" again, which is 100% Robusta with a WOW taste. You don't actually notice the caffeine because of the taste. Just after the second or third double you get a little shaky.
That reminds me of this morning: I didn't drink coffee for two days because of my stomach, and got me a double (30 or so % robusta) for breakfast. I was shivering for at least two hours after that