I quite like SPEE's battle system it's very final fantasy inspired and definitely gives the game a unique feeling compared to other Pokemon games.
BUT, one problem I always had with it is that it would
sometimes feel slow if the enemy team were high leveled. A lot of the
time you were just waiting for bars to fill up. It was an engine
limitation i could not get around.
But i've recently had a breakthrough in the form of dynaRPG patcher by Cherry. Now because of this, in 0.75 you can change the battle speed!