Some good reasons for using rail cuts are, they provide stability in rail, they make old school kickflips easier, they have less friction for rail tricks, and they wear out straight as opposed to a eventually curving. My experience with them was on the Andy Anderson deck (8.4375) A month into skating them I noticed that the rails were wearing out faster. It wore down to the 8.3125-8.375 range and in no time it became 8.25. This caused me to adjust the amount of spacers I had in my offset wheels more than I had liked to. In addition, they weren't wearing out perfectly even on both sides. one side was wider than the other. Its fair to mention that this board was 5 plies with some carbon fiber reinforcements blended in so perhaps that attributed to its faster wear. However, I believe that with a true bio-directional board its possible it could wear out more evenly.
As for how it worked in terms of doing what they are meant for, I'm not too sure if they made a difference. For instance, I did have my best days on coconut wheelies with this board, but I also had my best coconut wheelie wheels on that board so it wasn't the most fair comparison. As for did it provide stability in rail, I honestly couldn't tell. It wasn't night and day for me. I've heard people say rail whips are easier on them but I personally feel like its perfectly doable without them. And as for old school kickflips, I think for that trick its just easier with smaller decks in general. if a small deck had rail cuts it gives it a tighter traveling distance for the feet to flip. I don't think it did much on that board because the shortest point in the middle was in the 8.125 range. I wouldn't consider that "easy" just more manageable.
All in all, I liked them because they made a board that i thought felt too big feel smaller. this helped even it out. However, if you want a board that feels wider, unless you size up I think its better to not have them so you can have more foot room-not to mention they last longer. I'm curious if they only wore out fast because of the 5 plies and if the traditional 7 plies would slow down the process, as well as how much slower it'd be.