Jim and Walter have done an excellent job of covering the waterfront (Jim even quoted my criticism of the "Missouri Plan"!), so let me restrict myself to some additional thoughts they haven't addressed:
1) The George Soros campaign against judicial elections needs to be recognized as part of a larger campaign for judicial supremacy and the idea that judicial decision-making is beyond questioning by other branches of government, or even beyond disagreement from the outside world. As Jan Crawford Greenburg has noted, these calls for "judicial independence" somehow only apply to criticism of left-wing judges and judicial decisions; Judge William Pryor has refuted Sandra Day O'Connor thoroughly. It is also worth revisiting Judge Dennis Jacobs on the subject of judicial independence. Suspicion of Soros's motives in entirely proper: his vision and ultimate goal is thoroughly anti-democratic, which makes it all the more ironic that it is being implemented through the Democratic Party.
2) This is why it is important that critics on the right distinguish between bar-association-controlled "merit selection" and other means of appointing judges without elections. The Soros campaign against judicial elections is aiming for the former and for removing any checks on the judicial selection process. Jim already noted my earlier criticism of the "Missouri Plan," which I won't repeat.
3) One problem is that, even in the federal system, the checks and balances on judges anticipated by Federalist No. 81 have become completely eroded. It astonishes me that, with numerous Ninth Circuit judges acting lawlessly on a regular basis, the only Ninth Circuit judge right-wing groups have asked for the impeachment of in the last few years is Alex Kozinski. The opponents of judicial activism have ceded the political ground in the federal system. (The problem isn't helped when even Bob Barr buys into the left-wing Orwellian blurring of the term "judicial activism" to mean "judicial action," thus further corrupting the popular understanding of the appropriate role of judges.)
4) The soundness of the idea of lifetime judicial appointments is therefore missing the prerequisite understanding that judges who abused their power would be removed from office. Judges abuse their power without consequence. We are one justice away from losing the death penalty to judicial activism; one justice away to the Court ceding the First Amendment and the regulation of political speech to Congress; one justice away from stripping Second Amendment rights of any meaning; one justice away from authorization of government racial discrimination. That Obama claims to be reasonable on these questions thanks to recent conversions doesn't mean his appointments are going to be, and there is not anyone on the hypothetical Obama shortlists who isn't going to substitute their own judgment for the text and law of the constitution. As one who cares about the separation of powers, it pains me that Republicans aren't making this a bigger issue--these are all 70-30 issues, one of the few where the Republican Party has that sort of credibility with independents these days, and where their opponents do not dare state their views forthrightly.
5) I have mixed feelings about judicial elections in part because of this missing prerequisite and because of a second missing prerequisite. When a California Supreme Court unilaterally amends the state constitution or a Wisconsin Supreme Court announces that it will act as a super-legislature to strike down medical malpractice legislation because it disagrees with the actual legislature's conclusions, the judiciary has ceased to act as a judicial branch, and is just another political branch of government. As a first choice, I would prefer the judiciary to be a judiciary, but if it is not going to do so, then it is hard for me to see why the self-appointed philospher-kings should not be directly answerable to the voters.
6) But my feelings are mixed because, in practice over the last ten years, judicial elections do not appear to be a first-best solution. There have been successes against biased judges and judicial activism in the high courts of Texas, Ohio, Mississippi, Alabama, Illinois, and Wisconsin, but those campaigns largely focused on collateral or proxy issues, and not always entirely fairly. The voters were, for the most part, not participating in a debate about the appropriate role of the judiciary, and I doubt 1 in 100 Wisconsin voters understands the idea that Justice Butler misused rational-basis review. Even as a means to an end of getting better courts, I am skeptical. There were no successes in 2006, and it's hard for me to see why state judicial elections should be dominated by voter dissatisfaction with President Bush and Congressional pedophilia. Meanwhile, public choice theory teaches us that judicial elections are likely to be dominated by trial lawyers, which suggests that the election success of the last few years is not sustainable.
7) Even in the states where there have been election successes, the success of the business community has largely been limited to high courts, which have a limited ability to control the abuses of trial-lawyer controlled judges at the lower levels.
8) I think we have not seen trial lawyers fully respond to the threat to their livelihood from these successes, and am not convinced that their countermove will not ultimately be more effective. Mississippi, Ohio, and Texas high courts have had to reverse a lot of ludicrous pro-plaintiff decisions by lower courts, and left-wing groups are abusively using the resulting statistics to argue that the courts are in the pockets of business. The Soros campaign is going to have a big effect on how the media covers judicial elections in the future, and if there is buy-in to the "judicial independence"/supremacy meme, it will be harder to challenge abusive incumbent judges in the future.
9) An interesting test of Dan Pero's ideas about judicial elections is coming in his home-state of Michigan. The Left's support of "judicial independence" does not extend to judges who actually follow the Rule of Law and reject left-wing causes, and the left-wing Arcus Foundation is planning on throwing millions of dollars into unseating Chief Justice Cliff Taylor—and the campaign ads against him will write themselves thanks to the political attacks on Taylor from Justice Elizabeth Weaver, written almost as if they were in anticipation of this year's election. (See Jim's related post.)