I give up both alcohol and caffeine for one month every year. I've currently been off caffeine for 2 months. The most pronounced effect is by far the consistent energy levels throughout the day. It's an incredible feeling to wake up in the morning, before sun rise, and just be "ready to go"! You forget what that's like after years of coffee consumption.
I also found I'm much more aware of other folks who are hyped up on caffeine or needing more.
The biggest loss for me is the positive effect that caffeine had on my weightlifting capabilities (via incr blood pressure).
Ultimately I think giving up caffeine for the rest of my life would be the most logical decision; but it's not something I've ever even considered. Habits that act as crutches can have such a powerful hold on our lives.
I have, however, completely cut out alcohol so I sympathise with the bit about social situations. This was odd for me at first too. At certain evening events you are expected to have a drink at all times. I don't know why, but it's awkward if you don't have one. Water doesn't cut it. It has to be sparkling or brightly coloured or something. I discovered that I can ask for a lime soda pretty much anywhere and it's not too sweet and seems to completely satisfy the need for a drink. It's also cheap. I don't miss alcohol one bit.
As for the laxative effect of coffee, this is something I enjoy. I really hate the feeling I get when my bowels are not regular. The best times of my life are ones where I can set my watch by my bowel movements. It makes a huge difference to my life! So I'm glad if coffee helps me stay regular.