My experience has been mixed.
WB can be used by advanced players to get an additional advantage over their less skilled opponents. Examples of this usage include getting more advanced research at the start of the day, as soon as becomed available. Rushing a fort minutes before an attacker arrives. Sabotaging airfields seconds before a patrol or direct attack can happen.
This type of usage makes the game less competitive, helping players who are already winning to win more easily.
WB can also be used by less skilled and less active players. Because WB accumulate, they can be used once a day or once every few days, instead of in real time. This allows a less active player to start several units, and rush them to completion immediately. Same for building construction and research. It's an easy way to "catch up" on any action other than unit movement.
This type of usage levels the playing field, making it possible for less active players to survive a bit more easily against more active players.
Of course, activity is still important. It's hard to win when you ignore your army all day, when other micro-manage the movements of their units. But WB allow a player to negate some of this advantage.
