I can't say for sure that this is my favorite DLC, but it's up there pretty close. At first I didn't like it at all. I love the career scenarios are rarely finish standard ones. Several of the career scenarios are completely broken as far as their timeline goes. In fact, I believe only one works right. In one (very long at 210 min), the speed limit is set for freight but you are carrying passengers and the scenario thinks the speed limits are set accordingly.
There are also not really 12 scenarios. There are six, but both career and standard. The standard ones work perfectly fine of course as the speed limits don't matter.
The route is, at over 140 miles, one the longest available. It's very mountainous but still varied.
+ It's long! Takes several hours to run end to end.
+ Comes with quite a few different locomotives. That's better than most of the new ones that come with one or two. They are all reasonably well done and in the SP livery.
+ The route has some of the steepest grades I've been able to find anywhere in TS. There is a very short spot of 3.2% and longer stretches of 2.7 and 2.9. I use it frequently to weight test consists.
+ Two large train yards and many stops allow for a lot of possibilities when creating custom scenarios.
+ All achievements are possible despite career scenarios being broken. Simply drive through them and finishing will get you the achievements if you care about them.
- Broken career scenarios which DTG has refused to fix despite being told exactly how to do so by a forum member who himself made a fix. That fix somewhat mitigates the con here, but it's still sloppy work on DTG's part.
- There are several spots where speed limit changes are not marked properly on the HUD. There is one that is not marked properly on the track.
- There are a few buildings that could have used greater detail. Relatively minor, to me at least.
This route is also home to various interesting locomotives that are separate DLC's such as the Cab Forward and the Zephyr. If you like mountains, and don't care about the situation with the career scenarios (remember there is a fix on the workshop), you'll love it!
Note: The fix adds in new scenarios. You will see both listed in the possible scenarios to play. They are replica's with the speed limits fixed. I mention this as some may not find that adequate.