The main reason I started to use Linux was because at the time it was, and still is I think, much easier and more reliable to run GRASS GIS and other FOSS geospatial tools on Linux. An exception to that is SAGA GIS, which in my experience runs better on Windows (but admittedly I didn’t try out the latest release). People who are thinking about making the same step but are reluctant because of the perceived steep learning curve should consider giving the OSGeo LiveCD from the OSGeo LiveCD project a try. It is a “self-contained bootable DVD, USB thumb drive or Virtual Machine based on Xubuntu, that allows you to try a wide variety of open source geospatial software without installing anything”. In other words, it couldn’t get any easier than that. I am actually downloading the live CD to try out a few tools I haven’t installed yet.
For some other easy to install linux distributions with more or less up-to-date geospatial tools, check out this post.