This is, of course, a matter of opinion. My personal opinion on this is that the Constitution should not be amended in this way. Many states allow initiatives and referenda and (one can argue) their experiences show that this would not be a great thing.
The main problem is that initiatives lend themselves to the creation of laws that sound good on paper but have very negative consequences. People vote for them because they sound good, but the people do not know enough (because they are not professional legislators with staffs to do research for them, etc) to understand the ways the laws will impact things. For example, voters in California have voted to cut taxes and to increase the number of prisons and to decrease the size of classes in public schools. In other words, they have told the government to do more things with less money. All three policies sound good in isolation, but put together, they are bad for California.
Since the people do not have the time and the resources to become really well educated on all kinds of proposed laws, I think initiatives and referenda would be a bad thing on the federal level.