GIS at home

I recently searched around for opensource/freeware GIS programs that can be downloaded and run on a home computer. I was looking for real GIS that allows creation and editing of new data layers, not just GIS viewers that let you examine data that other people have already created. I finally secured a package called Quantum GIS, which installed and runs pretty well. Its analysis and editing capabilities are less than I would ideally like, however. I can create new vector layers but I have limited ability to edit them after they have been created (e.g. adding new attributes, altering polygons, etc.). It also doesn't have much analytical capabilty, and only modestly versatile symbology controls.

I tried to download and install full-fledged GRASS without success, though it's not clear to me why it failed. Does anyone out there have successful experience at installing and using GRASS or another desktop-scale freeware/shareware open source GIS package that has full editing and analysis capabilities? I would vastly prefer one that runs under Mac OS X (with x windows if necessary) rather than in windows. Ever since i got my Mac about a year ago I have grown less and less inclined to use Windoze, especially anything that requires installing and troubleshooting any new software (it's those antibodies that windows machines develop that reject new applications like bad organ transplants). I do have a fully equipped laptop with XP on it, if necessary.

Given that we only have 28K dialup internet access here, any of the interfaces that rely on remote internet data files (e.g. Google Earth) are essentially useless for me. I need something that uses files stored locally. I can download huge files on a one-time basis, but I can't use any application that requires continuous communication with the mothership and its data servers. {This means our homestead will remain blissfully free of Second Life!}

Suggestions/pointers welcome!