Never, actually. It always seemed too out there. Is it worth a look?
That and SimLife were pretty much scientifically based models of planets and biological systems. They were both quite difficult to play (you had to understand quite a lot) but very engaging. They definitely taught me a lot. But I don't know where you'd find them any longer.
When you don't know where else to look, eBay is a pretty good general purpose solution:
http://shop.ebay.com/items/_W0QQ_nkwZsimQ20earthQQ_armrsZ1QQ...
Have you ever played sim earth? I liked it a lot.