Not terribly for tomatoes. I suspect doing Nepenthes would be substantially more difficult. The key things are: 100% humidity, darkness, warmth, with a bit of airflow. The graft union CANNOT get dry under any circumstances; it must be kept in high humidity at all times until the plant has put out new growth. But don't think you can just wrap a wet paper towel around the union and cover it with plastic wrap, if you do that roots will grow and it won't work. Hence the airflow statement. The union has to fuse.
Failure to keep the union humid until new growth has been put out will result in immediate death. But if you keep the union wrapped (no peeking!) for 10 days or so and then acclimate the plant to plant-out conditions, you're golden.
It is easier than it sounds, but expect to lose several plants the first time around. Once you have a little experience, you can pretty much get 90% success every time.