I loved Geoworks--it was how I got introduced to GEOS and how powerful a good GUI desktop could be. I was so disappointed when AOL dropped support of it. :(
Geoworks kind of fell to the side of the road, but it still exists in some form at Breadbox.com: http://www.breadbox.com/
Like GEM, OS/2, Vision, Desqview, Geoworks kind of got killed by Microsoft bundling DOS and Windows to make their monopoly. By the time Windows NT and Windows 95 made it to the market, people went crazy over Windows and forgot the alternatives to it.