Today's Juniper announcement marks their entry into the Ethernet switching space, one which is dominated by Cisco. In my view, it makes enterprises think twice about procurement strategies which rely on a single vendor (Cisco) solution, with lost agility and poorer price/performance.
That said, Juniper will be challenged on a number of fronts:
#1 Enterprise is not carrier. Juniper has been successful in taking away Cisco share in the carrier router market, but their recent entry into the enterprise router market has resulted in a 1% share (according to Dell'Oro).