Cornell announced that arxiv overcome 500,000 submissions (see here). This is a key milestone. At this rate the threshold at 1,000,000 is expected for 2015. This is the undeniable proof of a great success and the evidence for a revolution in scientific publishing. Articles are all freely accessible. The future will say what other impact this will have. But already today we see a reshaping of all the publishing community to account for the very existence of arxiv.
I think this is the moment for cheers.