So, doing the 2 socks on 2 circs was interesting for awhile, back when there was all kinds of heel turning and gusset decreasing. Now I am at the foot and it seems like it is taking forever. At least I have an instep pattern to break up the tedium. I have to admit, though, that it will be nice to close both toes at once and finish these guys at the same time.
The first time I tried this technique, I found that all of my ends kept tangling and twisting, and it seemed I spent more time trying to unwrench the skein ends from the needles than actually knitting. Now that I've got the feel for this technique, I think I've solved this problem. I think I'd still be wary of doing stranded knitting this way (4 skeins at once...argh!). I've also heard that you can work 2 socks from the same skein: one from the end and one from the center. Frankly, the prospects of this sound frightening, especially considering you would be relying on the yarn from the center to behave itself, and they often don't. You would have no recourse if you ran into trouble, either, for you couldn't solve the problem by rolling it up into a ball.
There's a bit more futzing about between socks and at the ends than for just one sock, so I can't help but think that this technique is slower. I also found that having all of the heel and gusset stitches on one needle initially proved very unwieldy, as the initial ratio of instep to heel-and-gusset stitches was almost 2 to 1. When you have that much of a curve on the cabled part of the needle, it's much harder to get all of them onto the stiff part smoothly. Cat Bordhi knits her socks in profile (usually), and this keeps the number of stitches even on both needles throughout the gusset. Unfortunately, you can't employ this technique with 2 socks, short of migrating one of them off the circs and re-arranging the stitches independently.
There are advantages, however, to doing 2 socks at once. For one, the socks should have the exact same number of rows without any conscious thought put into it. This should guarantee equal fitting (assuming I measured properly). It also should cure Second Sock Syndrome (SSS), though this has yet to be an issue for me. Of course, if I screw up the pattern, I've screwed it up for both socks, most likely. I guess it's more likely to look like a "design element" than an error this way, though.
So, I think the verdict is still out on this technique.