I finally bought the GN Cascadian on June 8, and I'm having a blast. Seems to be the biggest route yet in my collection. Wonderful scenery, and it taught me how to drive steam trains. Already done a couple of scenarios, but I wanted to report something I'm not sure if has been reported already, since the route didn't have a widespread release.
I really like the "Griswold" signals at certain crossings, but I found two particular crossings at which the signals are bugged. The rotating banner is misplaced and it's actually floating over the track, looking very ugly. I noticed this at Wenatchee on the final crossing before you leave the town, and Skykomish on the station crossing. Still haven't ventured into the Everett extension. I have the route up to date with all the patches and the aforementioned extension.
Another thing I wanted to mention (but I admit I'm probably going into "nitpicking" territory) is that the main signals seem to have their "off" textures wrong. If you're stopped at a red signal, you'll notice the light that should turn green has a red glass cover, and when the red light turns off you'll see it has a green glass cover. They are mixed up. If you have the chance to see a blank signal you'll notice the color arrangement kinda looks like a traffic light, when the green aspect is actually above and the red aspect is below. I think the ground signals don't have this problem. Neither of these issues are game-breaking, of course, but they kinda detract from the otherwise great visual experience this route offers.