I've been pointed to a couple of toe-up with gusset patterns on Knitty: Baudelaire and Widdershins. Both of these are excellent designs, with extra levels of detail and patterning.
Me, I was on a plane at the time, without internet access. I was in the middle seat of the next-to-last row, no less. Sandwiched between two non-knitters. I got enough funny looks for knitting, but then when I took my shoe and sock off to try on my still-on-the-needles sock.... well, I think my seatmates were thinking about complaining.
What I learnt, other than that it's a mistake to take off your shoes in flight -- not because of any swelling, but that it's very challenging to lace up high-top sneakers in that small a space -- is that I didn't like the fit of the gusset-less sock.
So I did some thinking and drawing and hit upon it. Gussets are simply a section of the foot immediately below the heel worked on more stitches. That was easy. I ripped the foot back to inch before the heel, and added an increase on either side of the instep stitches every other row. I worked the shortrow heel on the original number of stitches, no problem.
The decision then was how to dispose of the stitches I'd added. In a standard-top down sock design, the number of stitches stays constant in the leg until after the heel is turned. But that's a flaw, too. The lowest part of my ankle is wider than higher up my leg. So it's not a problem to have a few extra stitches there - an upper gusset, if you will. It just doesn't need to be a long as the foot gusset. So I worked a decrease every round until they were gone.
And there it is! A double-gusset toe up sock. It fits great! Very pleased.