Going back to the original question for a moment, if the Classic Trains digital version is anything like the Model Railroader digital archive on DVD, I would probably advise against purchasing it.
The key reason: Resolution. (I'll skip the "proprietary format" discussion...)
I moved up from a 21 inch to a 32 inch monitor in the past couple of months. I <thought> that I would have an easier time reading the back issues of MR. Silly me. The scan resolution is simply not that good. Making the image larger does not make it "better." I'm no expert on this, but I feel like the scan images were made to emulate the actual size of the magazine and no larger. I am enjoying the look back (I'm up to January 1955, moving chronologically) but I would have liked it more if I could read and view the images more clearly.
I would check to see if someone local had a copy of the Classic Trains DVD and ask for a look-see before buying.