@radishhead: To tell you truth, they're not really that overpowered against Misty, you'll just get a less chance of your pokemon get KO'd. And besides, their's always having your Pokemon disobey your commands for having them leveling up too high... See, wich ever you choose, you'll still have a drawback. ;)
Salnax, I can't believe you didn't think of capturing the ones you don't have before grinding your party. XD