I get this question ocassionally so here is the offiical answer for the all too common question. Where can I view VAAI stats? Yes I'm sure you can find this elsewhere in the forums.
The most readily available area to view these stats is by logging in to an ESX/i console and running esxtop. See the following command sequence (and attached screenshot).
From an ESX/i console
u (for disk device)
f (add/remove fields)
bgi (remove fields)
op (add VAAI fields)
And wallah, see the attached screenshot, it should be identical if you are running 4.1.
There is a bug however when viewing. You will notice in certain columns that the numbers are "counters" and not "gauges" (RRD terminology). This means that the counter never decriments and is a continuous counter. The only way to view this data as a "gauge," or representation of recent data, is to either reboot the host or leverage powercli to view the stats and have it do the math for you.