In use daily for the past 2 weeks. I like it but it is not perfect:
1. I love the materials it is made out of because even though everything in our lives is plastic, I like to reduce as much as I can, particularly in what I consume and put on my body. This cup accomplishes that.
2. I need to get used to the silicone. It is pretty drip-free, but does drip from the lid (splashing at the rim) and drips under the sleeve. This increases clean-up time, since I need to remove the sleeve and wash it, too.
3. It is true, the sleeve gets warm and I would imagine if you take your coffee or tea black, perhaps too warm. Personally, I don't have a problem with this.
4. The glass is high-quality and as they warn you, it is slippery when wet. I've taken to putting the wet sleeve back on after washing if I'm walking around with it (I use at work so bring it back to my desk after washing)