I think it's unfortunate that they ended up having to market these heaters as energy savers - they really don't save that much energy, and in a lot of cases, end up using the same or more, AND using more water as well. The cold sandwich gets families to leave water running sometimes too long. Showers no longer have any real time limit. You get the idea.
That said, I installed a tankless about 4 year ago, and I love it - but for the RIGHT reasons. it's a lot smaller than my old tank, and it runs forever. I spend more on gas than I used to, because we just use the hot water a lot more. I actually would like to install a mini-tank heater and recirc line to get rid of the sandwich issue, and get instant hot water, which would pretty much eliminate all the negatives of the system.