Meiwa kumquats are very sweet. You eat these in one shot, skin and all. There is an intense spicy orange flavor from the zest (not quite bitter) but there is also an associated intense sweetness. The flesh is slightly orange-y flavored and both sweet / tart. When you eat the entire kumquat in one shot, it is a really fun eating experience.
Besides being delicious, kumquats are exceptionally good for you. Most of the nutrients and antioxidants in citrus is in the peel which is usually inedible. But with kumquats, you are getting a huge dose of vitamin C, and tons of antioxidants. So when you start to feel a cold coming on, eat a kumquat!