The recipe you have is fine. I agree with the "experiment" suggestion. A couple of things:
Use good coffee to start with -- makes a BIG difference. We store ours in the fridge to keep it fresher.
Your coffee maker probably came with directions about cleaning the unit periodically with vinegar and water. You don't have to be a fanatic about it, but do it every now & again. That will make a big difference with the taste and with how long it takes your maker to complete a cycle.
Yes, a little salt will mellow it out -- but if you use good coffee to start with, you won't need this.
Cinnamon is just for flavor. If my husband isn't going to be home, I add it in the basket because I like the taste. He's not a fan, though, so we don't make it this way when he's home (I can add some to my cup directly then, if I want to). Cocoa powder works the same way, as does nutmeg.
Another vote for using cold water -- and, yes, your water will affect the taste.
My husband sets up the coffee every night (I knew I loved that man for good reason!). Ours has a timer so we can just set it & have coffee ready when we get up in the morning. For us, the only thing that's almost as good as the first sip of coffee in the morning is the first sip of a cocktail or glass of wine in the evening!
Have fun --