While x86_64 hardware has been very common for years and it's now almost impossible to find new PC hardware that is x86-only, the Ubuntu download pages have continued to recommend the 32-bit version of Ubuntu Linux by default for new desktop installations. Fortunately, that may finally change.
At least once per release cycle the topic of "32-bit vs. 64-bit" as the recommended x86 version of Ubuntu Linux seems to be brought up. It's also brought up almost endlessly within Linux forums and elsewhere by newbies as they decide which flavor of Ubuntu to install on their PC. The past few release cycles looked like Canonical would end up recommending 64-bit by default, but so far they have only done so for the Ubuntu Server edition.
Today during the last day of the virtual Ubuntu Developer Summit prior to the Ubuntu 13.10 release, they discussed the 32-bit vs. 64-bit question once more. This time it looks like it might finally happen where from the Ubuntu download pages they will finally recommend the 64-bit desktop version.
With most PCs now supporting x86_64/AMD64, there really is no reason to be not using the 64-bit flavor assuming you have at least 1~2GB of RAM. There's significant performance advantages of using 64-bit binaries over 32-bit, as Phoronix tests so frequently show, including our already-published 32-bit vs. 64-bit Ubuntu 13.10 benchmarks
. Most previous x86_64 Linux limitations have already been addressed for years like Flash and Java issues, compatibility with certain drivers, and other bugs.
There was also some talk about when Ubuntu will stop being spun in a 32-bit flavor and go purely to x86_64 on the Intel/AMD side, but that still seems to be some years away for those with vintage PC hardware.
Those wanting to learn more about the latest 64-bit Ubuntu Linux proposal can see the session information at summit.ubuntu.com