Currently in tactical combat, you cannot select or interact with any of your units until a spell or ability particle effect is completely finished.  This is one of those little, easily fixable things that doesn't waste a lot of time all at once, but over time becomes infuriating and massively slows down the pace of the game.  This will be especially annoying during multiplayer when that becomes available. 

In the modern world of computing, a game should be capable of playing two animations concurrently.  I'd like to be able to start moving my cavalry forward before the last puff of smoke -completely- dissolves every single time.