I'll explain why I think it is a big deal in a little bit, since you asked. But real life is calling at the moment.
Yep, it is and the elimination of state control over the election of senators has resulted in senators being influenced by major lobbying groups. You want REAL campaign finance reform? Eliminate the 17th Amendment. Senators used to have to answer directly to their states. Now, as you know, big money donors from, say, California or New York can have a major influence on a state election.
Once a senator is elected, he/she practically has the job for life. The concerns of the state have very little influence on them any longer. Bring things home closer to the people.
They might sound familiar to you, since you are very familiar with the efforts of McCain.
Now, after the most protracted political battle in that usually bloodless revolution historians refer to as the Progressive Era, Secretary Bryan put his seal upon the reform that, in the expectations of those who had labored for it, would end the dominance of party "bosses" and the state "machines," stamp out the undue influence of special interests in the Senate, make it more responsive to the will of the people, and of course, eliminate, or greatly reduce, the execrable practice of spending large sums of money to get elected. (Source)I think it is abundantly clear that it has failed at each one of these goals, in spectacular fashion. There is a pretty good morning talking head on WRRK here in Pittsburgh named Jim Quinn. He has what he calls "Quinn's Second Law" which is that "liberalism always generates the opposite of its stated intent. I think a good case can be made for the 17th amendment having made each one of those worse.
Take campaign finance. By making Senate representation of states to be subject to popular vote, we created 100 more elections for special interests to funnel money into. Worse, quite often state races become national races, with special interests that have nothing to do with the state in question pouring money in to influence the election. Simply by repealing the 17th, the amount of money poured into the Senate campaigns would be minimized or completely removed.
Talk about campaign reform! If the special interests can't cause their treatment by the Senate to change with their contributions to election campaigns, then their incentive to try to buy things through the legislature is decreased. After all, why spend all that money trying to get the House to vote one way, if there is the Senate that can't be swayed by money thrown towards election ads or campaign contributions?
Aside from contravening the founders' purposes by removing the representative intermediaries between the people and the Senate, it is highly doubtful that the people were actually given greater control over Senate elections. Instead of selecting a trustworthy delegate from among his neighbors to negotiate the choice of senators on his behalf, the individual voter was now asked to rely on the second- and third-hand accounts of newspapers. At best, his first-hand knowledge of Senate candidates was usually limited to what he heard on the stump or in the rhetoric of debate. Because no state consisted of a single interest, and no candidate wished to alienate the particular audience whose attention he had momentarily been granted, the substance of such engagements would naturally tend either toward telling each group what the candidate thought it wanted to hear, or toward speaking in terms so broad and patriotic as to mean all things to all people.
Further, since Senate elections now are national affairs, the result is that the various elections often have less to do with the interests of the state, and more to do with the interests of the nation. This is a large change from the original intent of the Senate, which was to be the legislative body that protected state interests from encroachment by the federal government. The 17th amendment took the brakes that the states could apply to the expansion of the regulation state and the ever growing bureauocracy completely away.
Another problem of which most people generally agree is that politics have become too poll driven. The repeal of the 17th would be a nice step in the right direction at alleviating this tendency. Since a Senator who is appointed by a state legislature does not have to be concerned with his own popularity, his reliance on polls would be decreased. Instead, he/she would be more concerned with the support of his state's legislature- again moving control away from the federal government back to the states.
The Constitution set up a nice set of checks and balances. The federal government and the states. The three branches of government with each other. The two houses of the legislature (one publicly elected, one not) against each other. And the constitution was a check on direct democracy itself. The 17th amendment changed the balance of these checks, the results have been the opposite of what was intended, and it should be repealed (or replaced with something that says each state will determine for itself how the Senate seats for it are determined, be it by election or by appointment or whatever).