I think I will settle down with Todoist for a while after a long search of a to-do list app.  Although some functions are lacking, Todoist has many key features that I think a to-do list app must have. I am going to start with the pros of this app:

• Works on all platforms. I am a Mac fan using iPhone, iPad, and iMac at home. However, I have to use Windows for my work for many reasons. The fact that it works on all platforms matters to me. Todoist is the only to-do list app that has this flexibility among the three (OmniFocus, 2Do, and Todoist).
• Flexible attachment file format. You can attach all kinds of files to a task, with no limitations like 2Do. This is of importance when working on different platforms. I can attach a word file from my phone, and work on the file on a computer.   
• Relative cheap option compared with other cross-platform solutions. I am working at a University as a researcher, so I am qualified for the educational discount. I only need to pay $14.5 a year for one account. If I want to add accounts for my students, employees, or my spouse, I also only need to pay $14.5 for each account. However, the company just announced that they are going to increase the price for future users (from $29/year to $60/year for business users, and $29/year to $36/year for personal users). I suggest grabbing your subscription as soon as you can.  

Cons: 

• For the iPhone app, there is no passcode locking functionality.  I mean, seriously? I cannot set up an extra passcode for the Todoist app? This should be a default function for these kinds of apps which deal with sensitive personal information. For me, this is the only but huge concerns.
• No action function like 2do has. As I mentioned here, I think this function is really convenient and a must have for a to-do app. Todoist provides link function instead, but it is not as intuitive as the action function. For example, you can type tel: xxx-xxx-xxxx and it will become a link for making phone calls. But I cannot pick up numbers directly from my contacts. Typing adds chances of making mistakes. 

Just like what I mentioned, the company is going to increase the price starts from Dec 1st, 2018, and all the current users are going to pay the legacy price in the future as long as the accounts keep active. For the business accounts (including the educational accounts), the legacy price applies to all the current and future users. This is truly a great deal! I suggest to subscribe for one year before price increases, and you can decide whether you want to keep using it in the future. it would be good to open a business account because the price now is the same for personal and business users. By holding a business account, you can add new users for your colleagues or families with the same low legacy price in the future.