Prof,
I believe the neck knife is a great way to carry. I carry a Busse Assault Shaker and TOPs Night Chaser as neck knives one or the other every day 7/24s. As GG spoke of, you can always have it handy. I usually have a large folder or fixed blade on my belt, but he neck is always there.
I have found that is the most carried, but least used. Of course, this is because I carry the neck knife and others as well. If only the neck knife is carried, it will see all the use.
There has been some discussion regarding the use of neck knives around or in water. ie, Should the neck cord become entangled, freeing yourself could be difficult, or perhaps keeping your head underwater. There are nylon paracord sheaths with ball chain, which is supposed to break if grabbed or entangled that should solve this problem. I use paracord only.
Mike Snoody
Busse Combat
Rob Simonich
And a host of others all have neck knives.
Good luck