Spirits over 50%. Taste v effect I like a gin or 2, but tend to stick to the 37.5% stuff opposed to the stronger stuff.  I don't get any extra taste, just fall over quicker!  I understand that for some of the better whiskeys a little bit of water will bring out the taste.  At what point does the % become a problem for taste?
Your question is a bit broad because the flavour of high ABV spirits, and the intention of the spirits themselves vary widely.

Some alcohols with a high ABV, such as Hungarian Palinka, are sometimes drunk purely for inebriation. They have a high alcohol content mainly to cause the intended effects, not to produce a pleasing drink. These types of spirits are also often flavourless and used to make cocktails with alcohol content.

On the other hand, I've had Scotches that were as high as 60% but very easily drunk neat, and quite pleasing.

So in sum: whether and how someone enjoys a high ABV spirit really depends on the spirit and it's individual qualities.