Ubuntu used to be the big choice for stable Linux... but is it just me or have they been having issues with the last couple releases? I used to be a big time Linux user (LUG member, developer, etc), but lately I've been happy just using my Mac.
Ubuntu does have its problems. And these problems are being solved.
I'm no expert, but each of the four releases of this Debian Linux-derived OS I've used thus far has shown a marked improvement over its previous incarnation in terms of compatibility with a wider array of hardware, stability, performance, and ease of use.
That Ubuntu is available as a
live desktop install CD is a big plus in confirming its suitability for use with a particular PC before one commits to doing an actual install.
Beyond having Ubuntu download the restricted nVidia driver required to enable 3-D performance on the nVidia GPU-based display card I've equipped my current computer with, all of this machine's other hardware is fully supported--as was the case on every one of the 10 older Intel & AMD-based PCs I've run Ubuntu on.
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In contrast, Windows XP Pro SP2 (which I no longer need nor use) required numerous drivers to fully enable the hardware functions of machines manufactured from the summer of '04 onwards.
(Please note: Windows 7 looks pretty good from a performance standpoint. BUT, $320 for a Windows 7 Ultimate license

which can only be run on ONE machine?!

)
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That all being said, IMO when it comes to music production on a time-is-also-money basis, the Mac platform currently rules.
However,
Linux in general is a growing alternative for more PC users.
In my view...
A Mac is for people who have more money than time.
Windows is for people who have roughly equal amounts of money & time.
CLI-oriented Linux is for people who have more time than money.
GUI & CLI-based Ubuntu is for folks who are short of both.
