Hier die Antwort eines russischen Korrespondenzpartners:
Yes, "вызов" is quite appropriate in this context and can be used in most cases, but sometimes other words (or expressions) look more natural, for example "испытание", "подвиг", "препятствие", "трудное, но интересное дело", "проверка способностей", etc. The choice depends mostly on the style of writing and personal preference.
