Pepsi One has 1 calorie, 0g carbs, and is sweetened with Splenda. If you're a Pepsi fan, this is a good way to wean yourself off your sugar habit.
The flavor seems smoother and less acidic than regular soda. That of course is a good thing as far as I'm concerned - the horror stories you hear about acidic soda and your body are pretty much legendary. The flavor is nice and crisp, with almost a hint of citrussy flavor to it. That's always been one of the distinguishing factors between the Pepsi and Coke line.
There isn't any off flavor at all here - the smooth sweetness of Splenda shines through. Yes, there's caffeine, but you can only tackle your addictions one at a time :) The important thing here is that there's zero carbs, pretty much zero calories. It's incredibly critical that you get as much water into your body each day so that your body metabolizes well and loses weight (or maintains weight) properly. If you are simply bored of sugar and crave soda, this is a far, far better option than any sugary soda.
I of course highly recommend that you also wean yourself off soda long term - you really don't need caramel colors and chemicals in your body. But in the short term, if you're hooked on soda, this is definitely one to give a try to. I really don't see any reason that people drink sugary soda any more. Between the teeth destruction and other bad effects of sugar, the low carb / no carb options are sure winners!