Nikon @ Photokina day 1

In the same way that you don’t necessarily buy an f1.4 lens to shoot at f1.4 all the time, you aren’t likewise going to use the 25600 ISO that often either.

The fact remains though that the broader the useable ISO range gets, the more shooting options you have. That has to be a good thing, right?

It’s like a sports car. You’ll probably never drive your Bugatti Veyron flat out at 200mph, but all that reserve power means it will do ‘normal’ driving with far more control & composure.

@Landscape Photo.
Your name is the clue.
For landscape photography, you usually need HIGH megapixels and HIGHER F-Stop numbers (sat F16-22) to get a better plane of focus and if you came from shooting slide film, then you would be looking at shooting close to your old range of Fujichrome 50D, 100D, 64T and/or Kodachrome 25, 64, 200 and Ektachrome.
You used low ISO and shot mainly in daylight with polarizers, ND/graduated filters and such on tripods such as Gitzos or Manfrottos. You also used exposure compensation.
You seldom ever shoot at night or indoors.
WHEN indoors, people had to use very low F-stop lenses (F1.2 to F2.0) just to get an exposure, as they COULD not get usable results from anything above say Kodachrome 200 or Fujichrome 400D (even if they pushed it to ISO 800 and above) or they shot in black and white with Neopan 100, 400 or 1600 and the equivalents in T-Max at higher ISO’s or they even tried Agfapan 25 and various Ilford film for example.
NOW, when you do indoor concerts, candle lit weddings or other dimly lit subjects they used negative film and pushed it to ISO 1600 or above, if they could.
Now, in digital we have the equivalent of SLIDE film shooting at ISO 12,800 and thus you can shoot indoors with quality like slide and none of the crappy effects of print or negative film. THAT is why High ISO is so incredible, as you can shoot at higher shutter speeds indoors or outdoors and not worry about F-stop constraints as much PLUS get the higher depth of field and then action stopping speeds that you could not get before in slides or print film.
What does EV mean?
What are the equivalent exposure tables per each ISO rating?
If you know this and are familiar with handheld meters or photographic metering in general. you will get it, if not – then learn this and then high ISO becomes a clear advantage as it allows you to get pictures previously IMPOSSIBLE.