Been chasing Raikou for too long, and even though he's paralyzed and only has, like, 1 HP left, the damn thing breaks out of every ball I throw. I gave up for now and went after Articuno, the most difficult of the three birds at the moment. I started with 25 Dusk Balls and used six already. >_>
I've started collecting Gym Leader numbers, though, so I can get started on that, then start using the Elite Four to level up.
OMG. Stupid thing. I lowered its attack as low as it could go with Feather Dance, paralyzed it, lowered its accuracy as low as it could go with Flash, smacked it down to 1 HP, and when I began throwing Pokeballs at it... HOLY CRAP!! I threw 25 ultra balls and 13 dusk balls before I caught the stupid thing! Since I was very unhappy with that, I reset my game and went at it again. And guess what? Two dusk balls and I had it. TWO. GAH!! But yeah. That's my life.
When I finally got into catchable position, it took me only two dusk balls, as well. Freaky.
EDIT: Articuno acquired on the thirteenth Dusk Ball thrown. I immediately saved after.

