Who knows?

 Anyone wanting a full description of what John Kerry has achieved, praise or condemnation for one of the parties, must look somewhere else.

I am currently impressed with the variety of reports, couched as coming from one or another unnamed participant in Israeli or Palestinian governmental forums, with the additional reservation that some participants indicate that full details of the negotiations are not yet clear. We hear that both Palestinians and Israelis agreed to talk without preconditions, but on the condition that the Americans tilt quietly in one direction or another on key points. The talks said to begin sometime soon in Washington may deal with the terms of the discussion, rather than with actual negotiations toward an agreement. By some reports, there is no agreement. Prominent Palestinians are still saying that Kerry has to clarify the terms.
Anyone claiming to understand the paragraph above may be inclined to continue below.
As ever, I am primarily concerned with what is happening, and what is likely, rather than what should happen.
Among the reports is that Israel will release a number of prisoners, Palestinians will refrain from pressing anti-Israel issues in international forums, and both sides will keep talking for at least six or nine months.. 
I support peace and concessions. I recognize that details will remain hidden in order to buffer negotiators from political pressures. There are strong opponents of any concessions in both Israeli and Palestinian camps. I suspect that neither side will get all of its desires. I am far from certain that either side will get anything beyond what it has now, or that John Kerry and Barack Obama have made things better and not worse.
The American record in international affairs has been mixed, at best.
On the positive side is European reconstruction, 70 years of peace, and the European Union, no matter what we might think about individual decisions taken by that body.
On the negative side are the failures to protect South Vietnam from Communism or to bring democracy or even stability to Iraq, Afghanistan, Egypt and elsewhere among Muslim nations, along with all the deaths of Americans and others associated with those failures. On the list of presidents responsible for those failures and deaths we must put John Kennedy, Lyndon Johnson, Richard Nixon, George W. Bush, and Barack Obama.
Many would also claim that Jimmy Carter was responsible for the failed peace he hammered out between Israel and Egypt, but I see that as a major success. Sure, it is a cold peace, but far better than the continued need for Israel and Egypt to invest against the prospect of another war.
My guide is pragmatism, with an important component of benefit and cost analysis. Charismatics inspired by their reading of what the Almighty promised or intended operate on another stage, perhaps with a much larger audience, but hopefully not including the individuals who will decide on what this government or others actually does.
If Kerry''s process goes forward, it will have to overcome a number of well known obstacles. Perhaps the most prominent is the outspoken opposition to concessions in both national camps, including from those currently in control of the Gaza portion of Palestine. 
Also prominent is the posturing in both camps meant to negotiate only for the purpose of demonstrating that the other side is responsible for the failure.
And there are all the worrying points of violence and instability surrounding Israel and Palestine, with activists currently busy in Syria and elsewhere willing to direct their fire against any who violate their inspired view of what should be.
As far as we know, Kerry did not bring the parties to the point of agreeing on substantive concessions that would be included in a final settlement. He only brought them--maybe--to the point of agreeing to talk with one another. The Secretary is touting his success, but  there is the prospect that he has made things worse. If the prospects of talks lead the extremists in each camp to unseat the leaders who have agreed to the talks, or if the talks fail amid choruses on each side blaming the other, we may have to face more years of impasse, or an early escalation of violence. 
John Kerry and Barack Obama may yet join Jimmy Carter as making a positive contribution to the Middle East. Carter deserves his place for contributing to the peace with Egypt, despite the blots he has added to his record by latter day diatribes against Israel.
Political deals are inevitably imperfect. The calculation to be made is how imperfect, against the degree of imperfection in not accepting the deal.
For the time being, we should wait before chilling the champagne.