I've this list of seven reasons for Ubuntu's success that I thought were worth noting., but came across
The Linux distribution battle will come down to two distributions: Red Hat and Ubuntu. Red Hat is the market leader while Ubuntu is arguably the community leader (though Fedora is also coming back strong). How has Ubuntu managed to make such a significant impression on the market, despite its late start?
Having talked about a few of the other reasons on this blog, I'll call out two that I missed:
6. User promotion: Ubuntu is based heavily on the promotion it receives from its users. Nearly every person who uses Ubuntu today has been advised to try it by someone else who had tried it before them and so on. This, combined with the strong influence of Ubuntu to the Internet forums related to GNU/Linux, has led to a major increase in its adoption.
7. Fragmented competitors: When Ubuntu started its "march to glory" there were three "big" distributions, SuSE, Mandriva, and Fedora. Debian and Slackware were popular but were not very appealing to newbies (Debian still had a text based installer?). All of the "big three" were not at their best when Ubuntu came out and started gathering users. SuSE had recently been bought by Novell and was still undergoing internal reconstructions, Mandriva has in the middle of a severe financial crisis, and Fedora was just at FC2 which wasn't nearly as easy as it now is. This "fragmentation" (or "decay of the distribution maket" if you like) helped many users make the decision to switch to Ubuntu.
People may grouse about Mark Shuttleworth's financial contribution to Ubuntu's success, but I can point to many, many companies that couldn't buy success. Money is especially no guarantor of open-source success.
No, community is Ubuntu's capital, and it has invested this capital wisely. Ubuntu inspires the same sort of user passion that Apple does. This is why I think it, and not Novell, will be the biggest challenger to Red Hat's Linux dominance (though I don't see it displacing Red Hat - I suspect there will be a happy harmony between the two). Sun will play as well, but it's hard to bet against Ubuntu's momentum.