No, I had a SS thermos for years before the tumbler and it wasn't a problem either. I washed it out a couple times before I used it.
The thermos, (looks like a nikon lens from the outside) would keep the coffee warm for a couple hours at most. I can fill the tumbler up with coffee in the morning and it stays hot until afternoon. With hot coffee inside the outside stays cold. I think most of the heat loss is through the plastic lid. Cold stays cold all day long. I like to drink ice as it melts in the cup. The down side to the tumbler is it doesn't melt very fast for that use. :nono:
Thats the truth. I used to fill my mug to the top with ice and then add water. I did that with my TETI clone and drank the water and left thing sit in my car for 48 hours in the summer and I still had half a mug of ice. Now I put about 5 ice cubes in and add water. It stays cold all day. I don't notice a taste at all.