Just wanted to say "thanks" for all the info. Picked up used s1's and they are now voltmodded 
Why you dont prefer to buy 1 S3 for example? 366W @478 GH/s.
This tutorial is great but when you use 3 undervolted, would be better just 1 S3.
The advantage is, he's hashing with those Today. Undervolted S1's may not be as cost effective per watt as the S3, but the advantage is time. There are loads of used S1's floating around that you can buy right now, and even the earliest ship date for the S3 is 7/14 + however long it takes to get to you. Batch 3 is sold out, and no telling when batch 4 will ship. So if you missed the S3 boat, an undervolted S1 lets you stay relatively competitive before the S3's hits.
Yeah thats right. I have 2 S1´s right now mining at 400 GH/s together at 420W each i think because OC.... and waiting for 2 S3(im batch 2).
But once i get my 2 S3, i will sell my S1, but yeah right now if you just have S1, its nice to undervolt them, and its so easy and you safe a lot of power