Way belated damage control. I didn't think people were still reading this.

Disregard this topic. I found the CD shot on a review site, and since it was at full resolution, I assumed it was an adequate representation of what the CD version looks like.

The DVD version *is* bigger than GOG's download size, even with 7z compression. So I think we can still assume that the DVD version has higher quality something - likely FMVs.

DVD version looks way easier on the eyes. Hopefully they'll use that one.

Did you take these screenshots yourself? I'm very skeptical of the CD screenshot. It's far too blurry and doesn't even have a clean border (note the black along the top and right edges). Myst and Riven were compressed with something like GIF, not JPEG, and neither was ever blurry except during FMVs. Either that's a video, or it's not an untouched screenshot.
I have both the CD and DVD, so I'm going to look into this as soon as I can.
EDIT: Okay, using Ron Hayter's Riveal app I've extracted the same image from both the CD and DVD. I did not resave these or otherwise alter them - these are the original .PNG files.
If there's a difference between them, I cannot see it. I've also compared the various data folders, and as far as I can tell both versions use exactly the same files. They should look (and sound) identical.

I think it has to do with how the image is presented in-game.
I hope GOG is using the DVD version.

If you mean to suggest that the game engine compresses or otherwise alters the image quality, that is not the case. Those pictures are exactly what you will see in-game (plus black frame, inventory, and any overlaid videos or state changes).
Trust me. Riven has been my favorite game ever since the day it came out. I'm quite familiar with what it looks like.

My understanding is the audio was also improved for the DVD.
"Broderbund is becoming one of the first game companies to jump on the DVD platform, with a DVD release of Riven: The Sequel to Myst. The DVD version adds some new audio and video effects, a making of video, and manages to get the whole game on disc, as opposed to the CD-ROM version. Next up for Broderbund, a DVD-ROM version of Journeyman Project 3. "
from http://pc.ign.com/articles/060/060078p1.html

The original comparison appears to be from a video sequnce, judging by the water in the boiler. While your comparison is of the stills. If video was indeed improved for the DVD version this might explain the differences.

Hope they use the DVD version... I was dissapointed the last Tex Murphy game used the CD version.

The original comparison shots are clearly not directly from the game at all. They are both the wrong size, for one thing. And there is no full screen video at this location. The animations for the boiler window and the various levers are rendered individually and placed, when needed, over top the still image like decals - i.e. they wouldn't affect the whole image.
The only difference I noticed when I first played the DVD version was that one of the videos which previously had a bright pink compression artifact was clean. It was otherwise the exact same quality - just without the glitch. There may well be a few other corrections or tweaks, including new animations or sound effects, but I've never noticed them. The DVD was NOT a general upgrade like Myst Masterpiece was. I don't want people getting twisted up over which version GOG is using because I seriously doubt anybody here could tell the difference between them.
I intend to prove that as soon as I can, but it will require plugging in my old computer, and getting a little free time.

Do you wish to imply bugfixes and corrections are not important?

I'm implying that the GOG version, which will need to re-encode the videos along with other tweaks - opening the door for both new fixes and new mistakes - is likely to be more different from both the CD and DVD versions than the two are from each other.

Looking forward to Riven as well. Here's to hoping it's not as hard as I remember it being. I really want to beat it with no help.
Come on GOG, release it already! At least put up a date! I've got almost two full weeks off around christmas and this game is perfect for playing on my laptop while my wife and I watch TV.

I HIGHLY recommend a walkthrough for all MYST games.

I'm afraid Riven will be as hard as ever. Especially if you've had plenty of time to forget all the solutions in. :D
But why would you want to use a walkthrough? The fun is all in figuring stuff out. :(
Granted, I had to get help with the solution for the final puzzle, but that is so obscenely difficult if you don't know beforehand you're basically lost.
Solved all the rest on my own though. :D