Considering the vast array of training apps available, is TrainerRoads focus on structured workouts and scientific approach to training worth the premium subscription cost when compared to more affordable alternatives, and do the benefits of their training plans truly justify the investment for riders with varying levels of experience and fitness goals? What are some key factors that cyclists should consider when weighing the cost of TrainerRoad against other options, and are there any specific features or results that make it a worthwhile investment for serious riders?