So I just had my first Jake Shake today along with trying the 3 bars that came as part of the starter box.
I got the original small box and so far have had the 3 bars which were all pretty decent, not the most amazing thing I've ever tasted but very practical and not unpleasant to eat. The issue I had was when I tried the banana shake, it had a very granular texture to it and didn't seem like it combined with the water completely properly. It also left my feeling like the granules stuck to my throat and took a fair bit of liquid to get the feeling away. Due to this rather unpleasantness I was unable to drink more than half of it.
When mixing I used 400ml of cold water initially, then shook for about 30 seconds even though instructions said to do for 5 as I was a little worried it wouldn't mix properly. After this I tasted it and it felt very granular so I added another 100ml of water and shook for about 2 minutes, after which it still had a slightly less granular feel though still quite unpleasant.
Before making my next shake I wanted to make sure I didn't do anything wrong in the mixing process? room temp/warm water for example.
The flavor itself was nice just the texture made it unbearable in the end.