Day #1 for me as well. I've done the Master-Cleanse a few times (10/14 days), all have been positive experiences.
It'll be a bit tough this time with a holiday weekend and plenty of physical activity opportunities, but the Master-Cleanse is in order.
I've mentored a few friends of mine through first time fasts and they have all had positive experiences as well.
A good tip for the Day 1 folks: LIGHT PHYSICAL ACTIVITY! Do a walk, non-strenuous hike, easy bike ride every day. Have a glass of the Lemonade beforehand and keep another (I keep mine in empty 16 oz. water bottles) with you in case fatigue sets in.
I regularly practice yoga and have found it to be a great component to the fasting. After the initial 3 day adjustment, there is nothing (well, a few things hahaha) as great as a yoga class with energy and focus during the MC.