I think it's neat that it's 2010 and we still have no idea how we perceive taste. We were supposed to have hovercars and metallic jumpsuits by now and we still only have what can be regarded as a pretty basic understanding of our sense of taste. In the last year or two, though, the scope of what constitutes has expanded tremendously.
What we know of taste has thus far been largely observational. We know that taste and smell are inextricably linked since people who lose one also lose the other. We know that the mental constructs of tastes we create and store in our brains are plastic; they can be enhanced and revised by further encounters with a taste. We know our sense of taste can be tricked by chemicals that mock the flavors of foods. We know that there are five specialized taste receptor types; umami (my favorite), sour, sweet, salty and bitter.