Honestly (I'm probably not the best person to ask as I've tried nearly every bulk supplement on the market and have only found a few foul ones) it's not bad at all. Mixes fine.
Not sure what you mean mixes with - it's fine on it's own. Just make sure you take enough of it - saw a study yesterday in MD that we need 3 to 4 grams per day to get good carnosine levels inside cells.
No need to add histidine (the other component in carnosine - along with BA).
You just reminded me that I need to get some more of this stuff.