One of the big problems with a number of "fastest computers" has been that the speeds quoted have been obtained by using massively parallel processing. Programs that can work in this way have to be written specifically to use parallel processing efficiently. There's been much progress in this kind of programming; but it's still not a widely held skill.
So now instead of a weekend to write a program that takes a month to run, it will take a year to write the program that will run in a few minutes? It's progress if you'll need to run the same program many times (fairly likely now?). Or if we have a million monkeys each writing individual programs who will need to take turns at running them on the supercomputer (common a couple of decades ago?).
A story not too long ago about a hardware nut who claimed to have fixed up his mommy's computer so that she could download her movies at TByte/second rates causes one to wonder - what did she do with the downloads. There's NO MEMORY - and especially no hard drive - that can write that fast. Please pass the salt - a grain at a time will be sufficient.
In the context of what they're doing with it, I'm sure the news reports from Lost Almost are accurate; but they have little meaning or direct significance for most of us. As several have pointed out, it ain't your granny's computer (or even remotely like yours) that they're building.
And a PFlop computer probably isn't enough to make my Office 2007 run as fast as Office 2002 did before they disabled it with WinXP patches.