from a purely scientific point of view, any calculations or measurements can be corrected, perhaps with dificulty, to compensate for this proposal, if it is adopted. However, I didn't actually see any real justification for WHY the US wanted to make the change? I don't think changing something if it only benefits some users, at the expense of others, is a reasonable excuse.
The scientific community has an obsession with using absolute constants to define various internationaly used SI units. For example, the definition of a Metre is - the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second - where it was originaly defined as the length of a specific object (ref: http://www.gordonengland.co.uk/conversion/sidef.htm) The new, constant based, measurements remove the potential variations that could occur in the old, physical, standards, caused by changes in temperature, air preasure etc..
So now it appears that the US scientists would like to define a standard day. However, I don't really see the need to abolish leap seconds. I have no use of them in my work, but the fact is days HAVE been getting progressively longer for millions of years, as the rotation of the earth gradually slows down. If the new standard is adopted, will this mean that it has to be applied in retospective calculations on prehistoric events? Surely not, because the whole evolution of the planet, and it's natural resources, is heavily infuenced by these variable solar times in a range of ways,collectively known as Milankovitch cycles http://en.wikipedia.org/wiki/Milankovitch_cycles.
I can see the need to have a more regulated time for telecommunications or military purposes, but such a precise system is, I think, essentially artificial. Nature is just not so precise. Maybe there will have to be both a standard (solar), and absolute time measurement, in a similar way to the different 'true, magnetic, and geographical' north, that people use in navigation, and map reading :?