How to review the current state of open source vs. closed source graphics drivers?

How to know whether it's worth it to replace open source drivers installed by default with proprietary ones. Are there any benchmarks? Major known issues summaries. I don't mean 'at the time of writing this post'. I mean an up-to-date status on how the drivers compare.

This page https://help.ubuntu.com/community/BinaryDriverHowto/ certainly doesn't do much on the matter, nor it even mentions Intel. EDIT: I've just learned there is no Intel proprietary driver because they made their drivers open source https://askubuntu.com/a/17395/29347

Where to review the current state of Linux display drivers:
http://www.phoronix.com/
http://openbenchmarking.org/
Generally a brief lecture of one or two current articles on phoronix dealing with display drivers performance comparison will suffice to make a decision as what driver to install.

General situation in Linux display drivers - open source vs proprietary (doesn't change at least for a year):
Intel: only one driver line available - open source, good
nVidia: proprietary driver far superior / open source decent
AMD / ATI: proprietary driver far superior / open source - dreadful performance

Ultimately with Intel you're all set right after Ubuntu installation while for nVidia and AMD you don't install their proprietary drivers only if you absolutely don't need more than pure desktop tasks performance or you experience problems with said proprietary drivers.

As a buying tip: Avoid AMD/ATI

...when considering buying a rig for Linux. See What Linux Users Need To Know When Holiday Shopping For PC Hardware

December 2012 update http://www.phoronix.com/scan.php?page=article&item=ubuntu_raring_desktops1&num=1

It is my understanding that out of the three graphics card/chip makers (Intel, AMD, and Nvidia) only Intel has open sourced their drivers and continues to improve the open source version. The other two do not publish their source codes and only provides closed source binary blobs. I read somewhere in http://www.phoronix.com that Intel open source drivers are better than the closed source ones by AMD and Nvidia. Other than that, as @Goddard mentions, closed source drivers are better than the open source ones. Here is a more general comparison of various graphics drivers:

http://www.phoronix.com/scan.php?page=article&item=intel_ivy_gpushow&num=1

http://www.phoronix.com keeps publishing the latest about graphics drivers. However, some of these are about the very bleeding edge codes and are not immediately available in the user friendly form such as Ubuntu Software Center.

It is well known that the open source drivers are inferior to closed source drivers at this time.

Other then peace of mind there is no reason not to use closed source drivers, but people are working on it so hopefully that will change.

I read this article at the beginning of the year and your post reminded me of it. http://www.phoronix.com/scan.php?page=article&item=nvidia_june_2012&num=1

I am sure there are more reviews for say ATI related cards, but you can get a good idea of the current state of the open source drivers.

Hope this helps.