I've been using this for a while now.
Firstly by itself as directed on the packet. Its a bit bland with a fine paste/ gel like texture. Goes down well with no complaints, just bland.
The second use has been to mix it on-top of the normal Torq energy drink (two scoops in 500ml) at it's lower (160) rate, effectively having a double dose. I struggle to drink the 500ml/hr that torq recommends, so by mixing the two products together you end up with a higher carbohydrate drink, which is not excessively sweet (no sweeter than standard torq) and easy on the stomach.
From fast 4hr races to 24hr endurance slogs, that double mixture has served me well. Enabling me to keep the carb content up with less liquid intake, less eating (gels/bars) and zero stomach discomfort.
The only negative to this product is that the gel balls/paste cause the hydration pack nipple to leak slightly as they prevent it sealing.
Hard/soft water - Packet states that it shouldn't be used with water containing >40mg/l calcium hardness (most of the uk!). It mixes fine with hard (350mg/l) water in the SE. Having tried it on artificially softened water / brita filtered water and bottled water i can't see/taste any difference. Potentially there is a chemical reason for the difference, but its not visibly noticeable and i find that it mixes better than traditional drink powders.