Phoronix published a review on the Fedora 21 Alpha First Impressions: Its Great
A quote from the article:
While Fedora 21 is being dragged out agonizingly long for day-to-day Fedora users, the alpha release is out today and it's great and comes with many new features. Having not run Fedora Rawhide in several weeks now as the latest development code, Fedora 21 is turning out fairly nicely and with my early morning tests thus far the Fedora 21 Alpha release is stable and running quite nicely.Fedora 21 Alpha First Impressions: Its Great @ Phoronix