gamepro03 sums it up nicely. SaharaDrac does his own take in this 3 part video:
http://www.youtube.com/starcraftlega...82/w5rbwa3j9bM
http://www.youtube.com/starcraftlega...81/Cg9WBUfFMXg
http://www.youtube.com/starcraftlega...80/jY7pETeDEQ0
He also talks about "concaves" or what others call "surrounds" in attacks and defense.
His overall opinion on lifting for the gold early is it is a bust. This game is on Metalopolis, and golds have only 6 mineral nodes intead of the 8 at the main. This leads to 4 less workers to saturate.
Someone can correct my figures:
Main: 5 min/trip x 16 workers = 80 min/group trip
Gold: 10 min/trip x 12 workers = 120 min/group trip
This looks promising, but the extra income is caught up in defense spending. In the example video, the Terran player blocks off half the map with some interesting Planetary Fortress placement, but loses in the end.
From this video, the gold may give an early income boost, but between the time lost to move and the defense spending, the advantage is extremely brief, if at all. The better bet is to build up your main then expand to the gold first if you really want that boost.