I believe it will be pretty hard to train. Lets figure we'll be getting bonus exp for quests and such for summoning that come out. I imagine maybe some exp each TIME you summon the creature. The rest of the exp will likely come from the damage the summoned creature does. Which especially starting out wont be much at all. They said you start with a dog... *Blink blink* 0, 0, 0, 1exp, 0, 0, 0, 0... I can see it now lol. =P