Proprietary operating systems (OS's) are usually purchased with the hardware on which they are pre-installed. Linux, however, is generally downloaded and installed by the user on hardware of his or her choosing. Even for established hardware-software combinations, there is a chance that a component (e.g., video card, network card) will not function at first and require tweaking. The makers of Ubuntu Linux, thanks to a large library of drivers and supporting software, have improved overall hardware-software compatibility and led the Linux community forward in this regard.
As far as free and open-source software goes, Ubuntu is not the purest example of the form. It optionally includes a few pieces of proprietary software. Also, it is backed by Canonical Ltd., so corporate forces are at play. However, the makers of Ubuntu and the wider Ubuntu community have made great contributions to open-source movement — an undeniably positive thing, IMHO.