The straight on neck shot is the easiest shot if your going for the neck, shoot low you still hit neck shoot really low and you hit center of the chest, it's no smaller of a target than the center of the chest as he's looking at you, if you hit a little to the left or right chances it will be a clean miss, if that happens when aiming at the center of the chest your gonna hit one of the shoulders and never recover him, even if hit with an .06.
I have no problem hitting a 50 cent piece at 200 yds so a neck shot at a 100 is nothing, i think you owe it to your game to practice all you can and be very confident in your shots. It's really up to the one pulling the trigger, if you know you can do it go for it, if not pass the shot and hope he turns and gives you a lung shot . I for one will take it, and prefer it. I have been taking neck shots for around 25 years all with the .243 and never have lost a deer, and never had to track one from a neck shot. It's not the only shot I take but is about 85% of the time. It is not a marginal shot, it is the best and most humane way to harvest a deer.