I've loved this campaign since it was released back in the mid-90's, and I have purchased both the original when it came out, and the Revised Version, which was released recently.
First, production and value-wise, boht books are top notch. The Revised Version comes in a sturdy box, and is PACKED with gaming goodness. (I'd recommend the hard-copy over the PDF unless you're a complete digital enthusiast; you can get the set on Amazon for ~$75 bucks or so, which is only marginally more expnsieve than the PDF.
As to the Adventure itself...
A) Yes, it is potentially quite lethal, though, [excluding the Doom Traim Red-Herring in the prologue] they do a good job of ramping up to the danger, rather than throwing it at you right away. [Of course, lethality is dependent on the Keeper; in the introdcutory booklet, they offer options to keep players alive longer, including such options as simply "Doubling starting HP."]
B) The adventure is a bit railroady [pun-intended], though it's less noticable in this editon than in the previous version, to my mind. There's better connective tissue between scenarios, and the PC's get more info on some material that remained vague and behind-the-scenes in the orginal version. Most of the scenarios take place at cities where the Orient Express stops, obviously, and both editions largely hand-wave the trains schedule, opting for the more flexible "Trains are availabe as the Keeper sees fit" philosophy.
C) There are a few interludes on the train, along with cardtsock maps of the layout, and an entire book full of NPC's available for use. As Keeper you can add more or less time on the train as you see fit, of course.
D) Depsite the updates, there's still a few logical/plot gaps in the narrative, but, again they seem less obvious in this edition. (And the Keeper has Fenalik as a back-up should the PC"s utterly foul-up their mission and miss some of the Simulacrum pieces en route.)
That said, this is a rewarding campaing, but demands comittment from both PLayers and Keepers alike. And check out the recordings of actual-play from
www.yog-sothoth.com ; the Braford Players (*led by Paul McLean) are by far my favorite actual-play podcasters, see if this campaign sounds up your alley.