I tried only vdd1 and i think this only is a very big advantage.
I don't have numbers, but just for webbrowsing, idling, checking email and doing light stuff.
I think my battery life doubled

Vdd2 is unstable for me, after 1 night restart :/.

I downed the voltages also 1 jump, so 600 is on 54 and 550 on 48 and so on.

Let's see if this settings are stable for me for 1 hole day.

edit:

Normal on work i have 4 hours operation time, so fully using it, internet, little bit angry birds hihi.
Yesterday i could easy make 8 hours round and on home i still had battery, 1 hour driving with fm transmitter on, but home it was like 4mah hihi


Smartreflex > undervolting
I whatever case it's winning for me.
Only under full load undervolting is better, and full load i almost never use, i have no emulators or whatsoever and the sometimes the movies i check er max 1 min.

I need long battery live becuase overclocking even with undervolting kill my battery in a few hours.
On 600mhz with only undervolting is also nice but still smartreflex kicks it.