As long as you remember not to come to a complete stop, at an intersection, in 3rd gear, with cars waiting to turn behind you while you attempt to select lower gear but you can not. So always when downshifting, car needs to be moving at least a little. That is the only downside on the road, but than again there are too many positives to worry about any negative.
Enjoy the box. Once you setup your quick shift, up-shifting is a pleasure.