Todoist is a great To-Do list manager and it's biggest advantage is that is syncs across all my devices & applications - Chrome, iOS (iPad & iPhone), Linux, Mac. I love the reminders feature and the Karma feature.
I've been using Todoist for about a year and I've been loving it. I'm a premium member but I started off as a basic member and I wanted the premium features - so I decided to get the premium version - it's worth paying for it. I use it to track all my appointments, things I want to follow up on, daily stuff I want to do, articles I want to read in detail later. It can handle a lot.
I especially love the iPhone app - it's so easy for me to tick off tasks I've done and add new tasks on the go. I can also select multiple tasks and move them to another day if I've not been able to complete them.
Try out the basic version and let me know how you like it.
To learn more about how to use it, go to A Comprehensive Guide to Todoist
Note: All opinions are my own and I haven't been paid or given anything for free.