We use this software extensively at my place of employment and have done so for a few years. In fact, apart from ad-hoc spreadsheets with pretty coloured rows to make pseudo Gantt charts and the software developers using Gitlab issues, this is the only project/task management tool we use.

In short, it's quite good. It hasn't all been smooth sailing, but generally it's a solid piece of software which doesn't crash very often at all. The default design leaves a lot to be desired, but that can be easily fixed with CSS tweaks. Also, the performance can be very, very poor if there are a lot of cards open at once. The best process is to make sure any completed task is not just moved to a "Finished" column, but is actually Closed, so it no longer shows on the board. The Gantt chart (via a plugin, which used to be part of the core software) is a bit clunky. Exporting reports for management is also poor. Only a raw CSV export is available. There's also no actively developed mobile client. Overall though, I'm pretty happy with it for work projects, but don't use it for my personal stuff.