What are some alternatives?
When comparing Microsoft To-Do and Vikunja, you can also consider the following products
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Zenkit - Zenkit is the home you always wanted for your ideas, your projects, your business.
Asana - Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.
Remember The Milk - Remember The Milk is a task and time management application for mobile devices.
Wekan - The open-source Trello-like kanban (built with Meteor)
WeDo - WeDo is the best platform for planning and daily tasks management activities.