For a while, defection from the difficulties of Microsoft Windows involved broadly two choices - an Apple OS X notebook or taking the trouble to install linux yourself on a notebook. The latter was hard. Over the years, things got better with knoppix and then ubuntu, but it continues to be a hurdle. In my reckoning, once linux is installed and properly working on a notebook, it's roughly as good as OS X. But getting there is often daunting absent a friendly neighbourhood linux enthusiast.
A major development in this business is Dell offering a notebook with ubuntu pre-installed. This takes away the hurdle of knowing how to install linux. Here are links: Apple Macbook, and Dell ubuntu machines. In addition to the notebook, Dell has two desktops which have ubuntu pre-installed.
I configured a Dell notebook to be very close to the Apple (2 GHz dualcore processor, 1G of RAM, 80 G disk, etc) and it works out to $924. The Apple is $1100. So Apple seems to charge a premium of $175. There may be some differences: e.g. Apple says it has a 6 hour battery life while Dell is not obviously telling you what the battery life is; the Dell has a bigger screen (15.4" vs. 13"); linux is a bit ahead of OS X in terms of some pieces of technology (e.g. /proc) but a bit worse in others (e.g. USB). I have not been able to compare the mass of the two machines.
More interestingly, the entry level Dell notebook is at $600 and the entry-level desktop is at $400. That should attract many people, particularly in places like India. At Rs.40 per USD, $600 is just Rs.24,000 and $400 is Rs.16,000. The Dell India website does not yet have these machines but hopefully it soon will. Hmm, in a year or two, would we have a notebook at $500 and a INR/USD exchange rate of Rs.35 which multiplies to Rs.17,500? You could sell millions at this price.
So I think that for the first time, Apple has credible competition. You can now get another notebook - other than the Apple notebooks - with industrial-strength security, stability, flexibility, etc., where you open the box and start using it since the OS is pre-installed. As an aside, Dell has priced this notebook at $75 below the identical machine running Microsoft Windows, so the user saves money as well. All in all, very smart moves on the part of Dell.
Vikram Aggarwal points out that there have been difficulties with device support for linux. The Dell uses the Intel Integrated graphics, which has a full source code driver in the kernel and a driver written by Intel. As the open source ecosystem reaches commercial users, commercial motives will reshape the behaviour of many of the players.
Update: Vikram Aggarwal bought the new Dell notebook and has posted a review. He finds This is finally a Linux laptop that I can buy blindfolded.