Indeed, the histogram supports a visual way to make basic panel adjustments.
One interesting thing to note: "Exposure" is the middle zone, not the right-most zone.
(another interesting thing to note: "Contrast" is not accessible via the histogram).
That's because, once overall exposure is in the ball-park, it's primarily used for setting midtone brightness (e.g. to brighten midtones: drag exposure zone to the right, and if that over-brightens highlights, which it often does, then drag highlights zone to the left..).
To extend histogram all the way to right-wall, drag white zone right-ward.
Just one note: basic panel cautions and caveats still apply, for example:
-whites (dragging white zone leftward) is very ineffective (beyond 0) at bringing white point down, compared to -highlights (dragging highlight zone leftward beyond it's zero point).
So, my .02: if you prefer the visual method, then by all means - more power to ya.., but I still recommend checking the numbers at some point, since some PV2012 sliders work very differently in positive vs. negative direction, etc..
Bottom line: it's possible in PV2012 to have 2 histograms which look very similar but produce 2 very different looking images (of the same photo), primarily due to local contrast differences, but also saturation differences..
For example, if you have:
+exposure
+whites
(contrast depending)
-highlights
+shadows
-blacks
(maybe a touch of +clarity & +vib/+sat)
it results in a clear and contrasty image with articulated highlights and detailed shadows (enhanced local contrast). I like this look for many photographs - it's like having topaz adjust/detail built into Lightroom, except done better - hard to argue with (borderline HDR-ish, some might say). On the other hand, if you want an old-school photography look, with very little detail in the highlights and/or shadows, then you need to do essentially the opposite - the two may have very similar histograms, but a very different look and feel.
Rob