I've never found the treemap view of filesystem viewers all that useful. Pie charts aren't any better. A basic hierarchical list of directories sorted by size is fine. I can use it interactively and drill down if I need more information. Tree maps like this for example* seem to contain more information than I can easily process.
The one thing I like about that one is that you get a quick, rough overview of which file type (Applications, System, ...) use up how much space and where they are located in the hierarchy. But I don't generally care about the latter and the former would, again, best be served by a simple sortable list or tree list.
Daisy Disk for Mac is missing from this list (or maybe they don't count their visualization as treemap, but I think it is closely related and saw it categorized as such).
It's worth noting that Treemaps have shifted over time from maps that were often used to show complete filesystems with high-levels of depth, to visualizations that showed data one-or-two level deeps. This later kind in what you tend to see in newspapers and in financial data analysis.
If anyone's interested in generating Treemaps (especially of the later kind) I wrote a JS library to generate them after being frustrated how ugly all the existing off-the-shelf implementations were:
Personally I find treemaps hard to read, and for getting an idea of what's taking up space on a disk I much prefer pie charts like [1]. My favourite for Windows is Scanner by Steffen Gerlach[2]. I haven't found a good one for Mac yet.
There's a rough open source clone of Filelight for Macs[1]. Disclaimer: I'm the original author, but no longer involved.
A commercial app in the same genre, DaisyDisk[2], is much more flashy and polished. You can also get the KDE/Mac version filelight from MacPorts, as part of package 'kdeutils4'.
fsm (from SGI---you can see it in action in the movie "Jurassic Park") was an interesting filesystem viewer. It presented the filesystem in 3D on an infinite plane. Directories were squat boxes, while files were tall and skinny boxes sitting on directories. The size of the boxes reflected the size of the directory/file (huge files literally stood out). Color was used to indicate age---the older the file, the cooler and darker the color.
The one thing I like about that one is that you get a quick, rough overview of which file type (Applications, System, ...) use up how much space and where they are located in the hierarchy. But I don't generally care about the latter and the former would, again, best be served by a simple sortable list or tree list.
* http://www.cs.umd.edu/hcil/treemap-history/treeviz_colorful.... from the article