Railway capacity allocation in a deregulated market requires planners to solve a mathematically complex optimization problem while simultaneously arbitrating the wants and needs of different stakeholders. This paper analyses timetable quality from the perspective of timetable planners working for the Swedish infrastructure manager Trafikverket. Seven quality aspects are discussed: feasibility, disturbance resistance, competition management, capacity safeguarding, application fulfilment, attractiveness and compatibility with surrounding planning areas. Each aspect is introduced, including references to legal documents, development projects, and research literature. Further, an interview study with eight practitioners gives insight into the current state of practice in Sweden. The practitioners consider feasibility to be both most important and easiest to handle. Capacity safeguarding is considered least important, despite its prevalence in legal documents and envisioned process developments, and is also considered hardest to handle. In general, formal rules and guidelines seem important for emphasising the importance of a quality aspect in the planning process. To better support the planners in their arbitrating role, timetable planning tools based on mathematical optimization models could be implemented. For example, support tools could be used to analyse different solutions, and could unburden the planner from working with feasibility aspects by providing automatic conflict identification and resolution.