...savory. I have my doubts about the "6th taste" umami. Another topic, another time.
Tart taste seems relatively overlooked.
Salt - we know exactly how much we want. It could be a little less, a little more, but too much less or too much more and the food tastes awful.
Sweet - it depends on the context. Are we talking wine or Turkish delights? Again, not too little or not too much.
Hot - now, it's a challenge. How much chili pepper can you REALLY take, huh, showoff? It seems there's no limit for some people. Some people could do without it altogether.
Bitter is pretty much unexplored. Again, another time.
Now, sour. Have you ever had something so deliciously tart you wanted more even though it made your mouth pucker? How much more tart (tarter?) can you take?
I am trying my hardest to remember the name of an LA restaurant (a 2-syllable name - on La Cienega?) where I once had a whole platter of the tartest berry desserts I've ever had. It was pleasurable in a painful sort of way.
Severely tart things you've tasted? Liked, even?