I like that it's easy to set up my tasks (especially with their mobile app). It works well in combination with Google Calendar as its API integrates very tightly into GCal so you can easily cross-reference your calendar events onto tasks. Nothing really - just minor issues of getting things moving forward as quickly as possible without creating too many distractions from other work! Great tool when working collaboratively with others/teams who are spread geographically around different parts of the world. We're able to see what everyone else has been assigned next, get them started straight away if we've checked off something as being done ourselves or delegate those actions out if needed.