I'm biased.
I'm making a tool that's kind of like this one. Please keep that in mind, because I'm about to give a whole bunch of criticism here.
First things first, the UX and UI is really neat and there's lots of really good design and thought put into how fast the app is and how well it is handling a whole bunch of users. I was sitting in there with everyone in hacker news creating tasks and it was keeping up amazingly.
But my first impression using this is that it's going to need a lot more work on the depth of the features rather than the breath. It looks sleek and it's got lots of options on a task, but when you click through one of the options they are very bare bones. There is a depth of interaction that is missing.
One example, I click on the time to task option, and it gives me an option for repetition, but repetition comes in the form of day month or year. What happens if I want something to repeat every Tuesday, or every second month on the 5th? You just can't do it. You can repeat tasks, but because it's not powerful enough it's a system that's not going to be useful in a lot of cases. Taking my trash out happens every Tuesday. If I were to want to abandon my current system to use this app I would no longer be able to do that.
Another thing that struck me was the percentage/progress option. When I click the progress box I got a drop down list with increments of 10 which i could pick from. That was way less than I was expecting from a feature like that.
I have two criticisms here. The first is that I expected a progress system to be something of a system. Imagine having progress that is tied to the number of check boxes I've checked off, something that's not another manual thing that I have to click and keep track of.
But if it's going to just be a number entry, why is it only a number entry for progress? This could have been part of a bigger more powerful system that I can use to fit my needs. I'm not thinking "oh hey look I can keep it percentage", I'm more thinking "oh hey look I can't keep track of the amount of money I spent this week". Something as plain as a drop down with a bunch of numbers should never be a dedicated feature.
Percentage option doesn't hurt, but when you add little features like that instead of bigger systems, you're going to find that you get lots of people wanting to add new little features to fit their use cases. This will especially be true when the app is open source and everyone has the ability to go in and add that on their own.
Final criticism. There's a little bit of a disconnect in how you add a lot of stuff to a task. Take relations as an example. I click add relation, and nothing happens. I sit confused for a while, until I notice that the related tasks has already appeared in the main task window and now I need to click the plus in order to start creating a relationship.
All of those options in the right side bar which open items in the left sidebar could be in the left side bar from the start. When I click that button that starts the addition of relations to a task the app should start a process where I am now creating a relation, not popping up a new section. This way you have a direct connection between where I clicked to add a new thing, and the process for adding that new thing.
Everything I say here can be easily fixed, so it's not at all the end of the world. Don't take this as me saying the app is bad, but there are a lot of flaws here that make me hesitant to throw away what I've worked on.