The internal sleeve texture really does make a difference, way more stimulating than the smooth one I had before. The sound effect caught me off guard at first but now it's part of the whole thing and I actually like it.
Wasn't sure about the voice feature at first, but it actually adds a lot once you get into it. The internal sleeve has a good varied texture, and the different shapes clearly make a difference depending on how you use it. Ended up using it way more than I expected.