Well, there aren't many discussions yet, but SlashGISRS is using the same website engine. Where is the best discussion forum for GIS in the general perspective? I tend to spend time on the ESRI Developer Network (despite it's limited Java and Avenue coverage) or the Google Earth "BBS", but neither of those is really a general purpose site.
What makes Slashdot Slashdot is the community. There's enough people posting stories and commenting on them that it actually ends up getting interesting information fast. So, while using the same software is great, SlashGISRS (why the rs?) needs commenters and submitters to be worth going to. Aggregation without editors is the other approach, and there may be some smarts that can be put in there to keep the most interesting and recent stories up there, but that's not as easy as it sounds.