Hi everybody. I too am on thyroid meds. Have been for almost 10 years after having an overactive thyroid condition corrected. As Dragonwilo said, there's lots of variation in what is considered "normal" thyroid hormone levels. And it's very hard to determine whether your "normal" thyroid reading is appropriate for you. Sometimes the absence of symptoms is deceiving. Many people have low thyroid function and don't know it.
IMO the biggest benefit of thyroid hormone is that it helps to ensure your metabolism and the rest of your body are functioning properly.
On a side note, before my overactive thyroid was corrected in 1996, I had almost two years of "fun". Ate full meals every two hours but was always hungry and lost unbelieveable amounts of weight -16 pounds in two weeks. It was loads of fun until other symptoms started (elevated resting heart rate, heart skipping beats, etc). I tried to get my pcp the keep my thyroid in the slightly high normal range, so I could continue to lose weight without having the other unpleasant side effects. He wouldn't do it.