Thanks for the link to the thread. I think the link i provided earlier in this thread covers all and more of the negatives that ppl noted about the tankless systems.
The idea works well for some applications but i'm not certain it will work for us.

The two biggest pluses for tankless comes down to space saving (isn't a big issue for us) and saving energy (obviously preferred).
But the biggest thing we need to overcome is a lack of hot water to fill a jacuzzi tub with our present tank without compromising the availability of hot water for small applications like the dishwasher and washer. They don't use much water these days and i'm figuring if they pull water from the hot water line, but not enough to trigger the tankless system, or it takes too long for the tankless to supply hot water during the 30 seconds or so that our dishwasher (for example) draws water, then we would be always washing dishes and clothes in cold water even when a hot water option is selected.
I know people have complained about the length of time it takes to get hot water to the tap with a tankless unit, but i doubt anyone may have noticed if this problem carries over to the dishwasher and washer as well.

As a tradeoff, i'm thinking about replacing our 1999 Bradford White tank with a commercial, high performance tank instead:
http://www.johnwoodwaterheaters.com/EN/Commercial%20Products/Polaris-High-Efficiency-Gas.html

The Bradford has a typical input heating of 50,000 BTU/hr while the Polaris is rated for 199,000 BTU/hr, designed for small restaurant use (faster water heating recovery). With the unit turned up a bit higher providing more hot water / litre, i think this might solve the jacuzzi tub filling problem, while maintaining our present level of convenience with a tank system and yet possibly increase our capacity to recover hot water as the kids grow older and use the shower more often.

If we get to the point of having THAT much hot water used, the kids will either get used to cold showers, or if i'm feeling generous, i might consider a hybrid system where the tankless feeds the tank as someone mentioned earlier.
MAYBE.

Does anyone have any experience with a higher performance hot water tank like the Polaris?

"Those who preach the myths of audio are ignorant of truth."