Great product - we went through several time tracking apps on our journey to use Harvest and this is the best for us.
The Asana integration is wicked!
Whilst the UI is ever so slightly dated and some functions can be a little hard to find than they should be but on a whole it is, in fact, very functional and infinitely better than some pretty but clunky app.
Really convenient Mac app makes starting time tracking easy. Nice integration to Asana. And a rather nice Forecast companion app.
The UI is ever so slightly dated and the whole invoicing thing is a bit too controlling (we dont use it though!)