Fedora frequently runs the test-days for GNOME and the open-source Linux graphics drivers to find any new and outstanding regressions and other problems with the different software components. The reporting and fixes land back upstream so even if you're not a day-to-day Fedora user, it's useful to participate in these test days. The testing is also quite easy with a new LiveCD having been spun for the different test days.
Among the items to test out for GNOME 3.6 are various aspects of the GNOME Shell and various GNOME applications like Evolution, Epiphany, Empathy, Nautilus, etc.
More details on today's GNOME 3.6 test-day are available from Adam Williamson's blog, who does QA at Red Hat for Fedora, and then on the Fedora Project Wiki.