"If you like Lego and you like trains you'll find this set is amazing. Probably the best train Lego has produced for adult builders.
HOWEVER, there are two problems with this set that can lead to great frustration. Fortunately both of them can be easily fixed.
1) If you are planning on motorizing this set, when you get to step 53 in the instructions, stop and read ahead 65 pages to where they give the instructions for motorizing the set. You will discover that you can save yourself from 15+ min of building an interior that you will subsequently remove to make room for the motor. (if you are not motorizing it right away, go ahead and build the interior)
2) At least one popular youtuber encountered a serious design flaw that causes the train to derail, especially when running on the old metal track (9v track, discontinued 14 years ago), but what he didn't realize is that the problem is easily fixed. I too had this problem. So first let me explain what the problem is- when two wheels on an axle go around a curve the inside wheel wants to go slower than the outside wheel. For a non-powered train axle having red traction bands on both wheels can cause problems because the "grip" causes the two wheels to fight each other and in this case even contributing to a derailment. The solution is to remove exactly one red traction band from each unpowered axle. Ideally you should remove the red band from the right side of the first axle and left side of the last axle, but it will probably work if you remove exactly one red band from a given unpowered axle. In recap, you want red traction bands on all of the motorized wheels so the train will move, and then for the non-motorized axles you only want one wheel with a red traction band per axle so that the rods will turn and then for the other wheel on that axle make sure that it does NOT have a red traction band so that it can slip on the curves (don't worry about the smaller wheels, those already spin independently).
Other tips- if you are only building this set for static display, you might want to slip a couple of brown 1x4 bricks and a 1x4 tile into the gaps between the cab and each hood. There are also some clever tricks using 1x4x1 panels for hiding this gap when running, but you'll need to search online for those."