My wife and I were considering to replace 2012 Nissan Juke as our kids kept complaining about the back seat space. We loved Nissan Juke for its power - turbo charged 177hp - and it was faaaast!! Of course, powerful/fast means "eating a lot of gas" and Juke's mileage was more like 21 to 23mpg. We have done some research and finally obtained 2014 Prius v-three over the weekend. Kids love it as they have a huge space and the cargo area is amazingly big even with the big back seat space. We expected this but Prius is slow and we especially feel it when we merge into freeways. On the city streets, it is not bad. I guess it is something we will get used to. Overall, I love the smell of a brand new car and hope that Prius v will serve us for a long time.
Try the Power button if you feel you need more acceleration. It changes the timing, fuel, and electric power supplement. Really noticeable at a stop light or when merging, however you can get almost identical performance by flooring it when needed in the default Eco mode, which still maximizes mpg most of the time. The difference is you will hear high reving in this mode, which is not part of our automotive cultural expectations. Hopefully you are not coming to a dead stop at the top of the freeway ramp; that is not a good driving strategy in any car. You get used to it just as you get used to over 400 miles on a 10 gallon fillup.
I hope you enjoy your Prius as much as I have enjoyed mine. All the power an adult could need, just not all the power a boy could want.
Just get accustomed to flooring it. The power button won't make any difference, just floor it if you feel the need.