I know this answer isn't tea or coffee, I don't like coffee and I gave tea up because it was staining my teeth.
I was on herbal teas for a while but I then had the idea of drinking a weak beef stock (1 stock cube to 1.2 litres of water) and I love it so much I can't go back!
I thought I'd miss that caffeine but it was very easy to give up and I really don't miss it at all!