This is a dream come true. I always (now and as a child) wanted to have a model of this fascinating vehicle. When my "dark ages" were over, LEGO just started releasing their Star Wars sets, and I found all those great custom models on the net.
At that time, my amount of light gray bricks wasn't very numerous. Although I had seen the pictures of Shaun Sullivan's AT-ST, I decided to build Bram Lambrecht's rendition of it, because he had provided instructions for it on the net and I never thought that I could build Shaun's version with my brick supplies. Then I came across some pictures of a Star Wars scenery (NETLUG at MIT Mindfest '99) featuring two AT-ATs (one by Shaun Sullivan, the other by David Eaton).

At the same time a LEGO truck stopped at our local TRU to promote the new Star Wars sets. Inside this truck also was a scenery featuring (among a small Death Star and a Star Destroyer) two giant AT-ATs.
But I never ever thought that I would have such a model myself some time, because I simply didn't have enough (light gray) bricks. But then I found a guy who was selling individual LEGO parts, so (still having the AT-AT in mind) I crammed my bags with lots and lots of gray bricks & castle slope parts until he stopped me. Back at home I rendered a few pictures of Iven Connary's great 3D model to use as additional reference.

Although I took the dimensions of the main body from Shaun's & David's models, I tried to build as much as I could using my own ideas, including the head, back and feet.

But sometimes it was simply unavoidable to copy some of their great ideas.

The neck consists of four 5571/5563 rims and due to a special mechanism (see pic on the right) the head can be put in (almost) any position.
At first the legs had "knee joints" (using the "new" #30364/65 hinges), but for the sake of stability I made them stiff later, so the model was able to stand on its own.
Model dimensions: length: 65cm, height: 55cm

On the right is Bram Lambrecht's original AT-ST. Later, when the instructions for Shaun's AT-ST were available on the net (and I had acquired even more gray bricks), I decided to built his AT-ST to go along with the AT-AT.

And now he has updated his rendition of the AT-ST to an even greater revision 2.