The ability to do in-app estimation is great! I can estimate what should be my next sprint in the context of how long it will take me to finish everything. This makes estimating much faster than with paper/pencil or even Excel. It's not as easy as you think at first, but once you get used to it, it's actually quite fun!! You can try out some demo projects to see if this fits your needs before making the complete switch. In my case, the project we are working on needed us to estimate user stories for multiple products so I am able to give estimates to other product managers (or PMs) which helps me keep everyone informed about our progress.