E.T. Jaynes had a brief exchange of correspondence with Hugh Everett in 1957. The exchange was initiated by Everett, who commented on recently published works by Jaynes. Jaynes responded to Everett's comments, and finally sent Everett a letter reviewing a short version of Everett's thesis published that year.
Jaynes reaction was extremely positive at first: "It seems fair to say that your theory is the logical completion of quantum theory, in exactly the same sense that relativity was the logical completion of classical theory." High praise. But Jaynes swiftly follows up the praise with fundamental objections: "This is just the fundamental cause of Einstein's most serious objections to quantum theory, and it seems to me that the things that worried Einstein still cause trouble in your theory, but in an entirely new way." His letter goes on to detail his concerns, and insist, wtih Bohm, that "Einstein's objections to quantum theory have never been satisfactorily answered.
The Collected Works of Everett has some narrative about their interaction:
Hugh Everett marginal notes on page from E. T. Jaynes' "Information Theory and Statistical Mechanics"
Hugh Everett handwritten draft letter to E.T. Jaynes, 15-May-1957
Hugh Everett letter to E. T. Jaynes, 11-June-1957
E.T. Jaynes letter to Hugh Everett, 15-October-1957 - Never before published
Directory at Google site with all the links and docs above. Also links to Washington University at St. Louis copyright form for this doc, Everett's thesis, long and short forms, and Jaynes' paper (the papers they were discussing in their correspondence). I hope to be adding the final letter in this exchange, Jaynes to Hewitt 17-June-1957, within a couple of weeks. , and maybe some documents from the Yahoo Group ETJaynesStudy as well.
For perspective on Jaynes more recent thoughts on quantum theory:
Jaynes paper on EPR and Bell's Theorem: http://bayes.wustl.edu/etj/articles/cmystery.pdf
Jaynes speculations on quantum theory: http://bayes.wustl.edu/etj/articles/scattering.by.free.pdf