It's just as good. I've only really had to use the wall one at the weekends, the half hour or so in the car with it on the Dashcharger on the way to/from work each day has been keeping it full.
I'd love to give it a go. I've bought several car chargers over the past few years and found them all to be crap. They just maintained battery when using sat nav etc. I invested in a better quality one a few months ago. It does charge, But only a few % in a 25min commute.
Would this really make a huge difference? How much is it down to the car as well?