I switched to decaffeinated coffee a couple of years ago (why?[1]). I was drinking about 250mg worth of caffeine a day before I stopped. I had a week of bad headaches, interrupted sleep, night sweats and crankiness and I was done. It's not nice but it's only a week or so. I avoided taking painkillers to mask the symptoms as some contain caffeine (especially the "Express" versions) to speed up the body's metabolism and get them into the bloodstream quicker; suffering the full symptoms also serves as a reminder of why I was doing it.
Decaf still contains some caffeine, so my 5 cups a day are probably still giving me ~25mg or so of caffeine. I drink it because I like the taste of coffee although I'm considering giving it up completely. I'm not a coffee snob and I'm happy with the taste of instant coffee.
25mg is still less caffeine than is contained in a single can of Coke (36mg).
Years ago I stopped eating chocolate and drinking soda for both dental and health reasons (I want to avoid the increased risk of Type II Diabetes from large intakes of sugary drinks).
I still, once a week maybe, have a non-decaf coffee if decaf isn't available, but I try to limit myself to one that day as I do notice the buzz from having a full strength coffee again.
1. Primary driver was in preparation for some long distance cycling where I'd be getting <10 hours (in total) sleep[2] over 4 days. I needed caffeine to have its old effect of giving me a temporary boost in case I was a few hours from somewhere where I could comfortably get some sleep[3]. Secondary driver was that it's a pernicious drug that I wanted to drop any dependency on.
2. I cope with sleep deprivation very well, indeed I coped a lot better with lack of sleep than a lot of other people on the event. Having children is good training for sleep deprivation (or at least not getting more than 3 hours sleep in a single stretch).
3. My planned naps (one or two hours a day) staved off most of the problems but I did get caught out a couple of times. One was at night and so I loaded up with coffee (many locals along the route set up roadside stalls giving out free coffee and food to riders) to keep myself awake for the three hours to the next control where I slept; the other was during the day when it was nice and sunny so I had an hour long nap on some grass by the road side.
When I'm coming up to weightlifting competitions I wean myself off coffee (by progressively substituting regular coffee for decaf in my espresso machine) for the same reason: I want to increase the effect on mental energy, but not have the side-effects such as sweaty hands or shakiness.
