Estimates on Linux marketshare have been notoriously hard to make, given that it’s no a commercial product, but typical estimates for a home user is pretty much always under 3%. Apple has had a nice boom in the past couple years, pushing up towards around 8%.
On push for seeing Linux as a more widespread option is courting OEMs to provide the option of purchasing computers with Linux preinstalled as opposed to Windows, which would naturally allow the system to come at a low price (at full price, the Inspiron Mini 9 from Dell comes in at $100 less). Most prominently, Dell has provided various options in this vein to various degrees of effectiveness.
Lately, though, the primary marketplace has been for the recently popular Netbooks. How popular? Well the numbers are in, and for the Inspiron Mini 9, Linux comprised 33% of all sales.
Regardless of position on the Operating System, more significant competition in the OS retail space is definitely a positive. Dell netbooks come with a modified version of Ubuntu, but don’t forget about Mandriva 😛