To be honest, this route is very hard for me to reccomend.
-Lots of engines. The variety of SP engines is wonderful, you can do a lot with what you're given, and if you need more, more is provided as additional DLC.
-The route is highly detailed. It does look and feel like the sierra nevadas.
-Large yards at both ends of the route allow for lots of switching.
-Has a good presence on the Steam Workshop.
-maintaining low speeds is a really good challenge on the mainline
-This route is very buggy. Aside from some scenarios not working properly (I once got an "invalid consist" glitch after spending a good 90 minutes on a career scenario), along with this, I've come across a few invisible buildings, and many signals along the route, for me anyways, have invisible stands, that cause the signals to float midair, which can be really distracting and immersion ruining, which is essential for a route like this because...
-scenarios are really really long. There are very few towns along the route, and with the exception of Sparks and Reno, they are all very spread apart. Due to this, the scenarios included take very long to complete, and are actually kinda boring after a while.
-this route is NOT beginner friendly. at all. I still have no idea why this was included in the TS2014 package, but this route is really really bad for people new to train simulator. Because of the sheer length of the route, how long scenarios are, and how difficult it is to manage consists going up and down really rough slopes, this route is incredibly difficult to get the hang of without prior experience. Plus, the low speeds will get incredibly boring for new players.
-Honestly, not a fan of the overall look of this route. Its really really brown, IMO. It doesn't look unrealistic, its just not a very pretty route.
-There is almost no change in scenery at all. Its literally all just big brown mountains. There is no variety at all with this route, you start in the mountains, you end in the mountains. This may seem like not that big of a deal, but trust me, after staring at mountains for hours at a time, you'll beg for something different.
Despite all this, I would reccomend this route for one thing. The Southern Pacific Engines are pretty good, and if you want to run them as unpatched locomotives on any UP route, you'll have everything you need. Unless this really appeals to you, I would not reccomend this route to you. I would CERTAINLY not reccomend it unless you're already an avid North American Freight RailSimmer, are new to Train Simulator, or this is the first time you've ever heard of "Southern Pacifc".
If you do want to get into North American Freight, I would direct you to lots of other routes, mainly Marias Pass, but unless you're really into SP, you should buy something else.