One popular website, Ammon, carried more than 200 messages.
"The best news I heard in two years - our political life was in a coma and this measure was necessary," a man calling himself Irbidaoui wrote.
Dozens of readers said the royal decree was the "best gift for Eid" - the Muslim Feast of the Sacrifice which starts on Thursday in Jordan.
Time for change?
Jordanian media have reported increasing political wrangling between pro-government MPs and the Islamist and leftist opposition over an electoral law and constituency boundaries.
But it is not clear now if any changes can be made before the early election.
Only six of the 22 candidates fielded by the Islamic Action Front (IAF) were victorious in the last general election on November 20, 2007, a tally sharply down on the 17 seats it won in the previous polls in 2003.
After that vote, the IAF - the political wing of the Muslim Brotherhood - claimed there had been widespread vote-buying in some constituencies despite pledges of transparency from the government.
Even in their traditional stronghold of Zarqa, an impoverished city east of the capital Amman, the Islamists failed to win a single seat.
The IAF withdrew all of its candidates from municipal polls in July 2007, complaining that there were insufficient safeguards against electoral fraud.
It is the second time the king has dissolved parliament early since he acceded to the throne in 1999.