Hell yes. I totally cut caffeine (as well as all sugars and grains) for the first four months I was Primal. Sugar? Pah! Who needs it? Grain? Whatever. Don't miss it at all. caffeine? I thought about coffee for every single day for four months. Eventually I said 'fuck it' and reintroduced the wonderful stuff. At first I was just two in the morning, and that was better than nothing. Over time however my intake has crept back up. Still down from where it was (maybe 3-4 large mugs a day).
I find it works wonders on my mood and mental acuity.