The flick serve is a must to have in your armoury of shots. It must be deceptive and undistinguishable from your normal low serve (notice that I don't call it the short serve !!)When I was a player I would always flick at least once in the first few points just so that it would keep the receiver honest and normally keep the pressure off my low serve.
But not only is it important to have a good flick serve but it's also important to be able to play it as a receiver.
Shots and footwork are constantly being added to, if you have watched any international badminton recently, you will see that for the flick serve when receiving the receiver's footwork is simply a couple of steps and a short jump backwards to try and hit the shuttle down or at least flat and hard. Most of the time they were off balance when hitting and their recovery was minimal (poor).
Their priority was just to hit down even if the shuttle was slightly behind them, they had no time to do a few steps then a scissors jump. Watch the chinese especially in the Sudirman cup their only priority was to hit down from the flick, their footwork and recover was in a way secondary but obviously practiced.
This is what I will be coaching this weekend to my players, they will not only be practicing the flick serve but the receiving also, then they will practice going forward for the low serve then reacting for a flick. The main objective to be hitting the shuttle down in the shortest time possible. Looking good and recovery will be secondary but also practiced.