I know a guy...
Here's the general skeleton:
And here's what the semi-finished inside looks like (you can see the far end of the roof with no insulation, then insulation, then covering):
And this is the finished product:
Eventually I may insulate the walls, but it has a silver roof and is in a shady area, so it doesn't get too hot, even with these 100 degree days. I have a woodstove which will heat the whole thing up to about 65 degrees in an hour or two, so heating is not an issue.
I really like the steel trusses because of the simplicity and how much clear height you get. I built mine at 13'6" at the walls, which gives me about 16' clear below the truss straps (center third of the building), and about 19' at the peak. From a cost perspective, you can do wood trusses a little cheaper, but I wanted the ceiling clearance. Also, I got my trusses used on craigslist for 1/4 the cost of new, so it was a no-brainer.