I'm not sure if it would be accurate to characterize the Model 39 as troubled. It actually first came on the scene about 1954 as a result of S&W response to the government exploring the possiblity of replacing the M1911. The design goes back to the late 40's early 50's and for many years the M39 was a real sleeper in the S&W line-up but that started to change in the 60's. It is true that some gun writers in its heyday were not very complimentary to the pistol. True, there were problems with the extractor which brought about a change and the Model 39-2 designation. There was, I believe, too a change in the feed ramp with the 39-2 and this had to do with the Illinois State Police adopting the M39 as their service weapon circa 1967. They were the first agency to issue a DA auto loader in quantity. At the time, the ISP was using a 100 gr 9mm Winchester Power Point load (later abandoned for more efficient ammunition in the stopping department). The DA pull was stagey and heavy, but not anymore so than a P38 (it's only real competitor in the DA 9mm market at the time).
Great looks and great ergnomics made the M39 very popular with me and over the years I have owned five M39's. and currently have two in my collection, one ASNIB from 1972 and one that has been well used with the fully adjustable S&W factory sights (the so-called "lollipop sights" which were available from S&W only as an after-market item; most will recall that the M39 standard sights were adjustable for windage only) I also have a 539 with adjustable sights (the fixed sight models are harder to come by) also ANIB. The M39-2 that I use as a shooter, shoots well and I have never had any real problems with it. I'd love to have an M639 with fixed sights or adjustable sights in any condition!
Even in 2008 I wouldn't hesitate to carry one if I were going to carry a 9mm.
I will pass on a tale which I cannot confirm and asked Roy Jinks about it, and he was unfamiliar with it and there is no factory proof because of the way, he said, government contracts were written at that time: Back in the original Mercury Space Program when the astronauts did soft landings in the ocean, Soviet ships always monitored the landings and there was a great fear that they might try to capture a space capsule and perhaps and seize one of our astronauts (this may sound far fetched to some of you but it isn't any wilder than some of the contemporary scenarios I've heard since 9/11 from official sources...and this is the way we thought in the Cold War and planned for any contingency, so from my perspective, it is not implausible based on my own experiences during that time in our history). Anyway, supposedly NASA issued M39s to the astronauts for personal protection in case the Soviets got to the capsule first. If that's so, the S&WM39 was the first western firearm and maybe the first firearm (I don't know if the USSR armed its cosmonauts) in space. An interesting tale, but to repeat, without verification.
Mark L.