The storage shelf project I used as justification to buy a welder is now complete. (and I ended up with a second new welder as well). Here's the project told in pictures....
I went with a design that allowed me to build separate units and then I bolted them all together for stability. I used no diagonal cross bracing and when free standing, they would wobble a bit because of that. Still, they were plenty strong enough tho allow me to climb them even when free standing without fear. If they were to be used free standing instead of bolted into a larger structure, I would have added some cross bracing.
It was certainly a lot of work, and hard to justify if the goal is to save money. Only if you could get the material at a large discount (or free) could you justify the project on a cost basis. However, for those of us that just love designing and building or own custom stuff, it was a great project and I'm very happy with the result (the wife is too).
It was also a great learning exercise to develop my fabricating skills. Nothing very complex, yet plenty of mistakes to make and tricks to learn along the way. It would be a good first project for anyone just learning to weld.
As my basement project continues, I'll probably end up building some more shelves of the same design, and who knows what else. I can't wait to get the basement done so I can move on to building my new shop area. But it's all going to take a bit of time and other work I've been ignoring as I played with my new tools calls....
Thanks everyone for the advice you all shared on the project.