Oh yes, Pikachu! <3
Extremespeed might give some utility in denying revenge kills, but seriously this isn't very usable. Because of the way Light Ball works, you need to fully invest in your EVs in order to have high Special Attack score (or high Attack score). That means you;ll split EVs and you can't take any EVs from speed because Pika needs all the speed he can get. This might make a physical set a lot more viable, though: I think this is what Nintendo's aiming at since DPP, ya know. Volt Tackle, its strongest STAB, became physical and Light Ball started to raise its attack as well. A small tidbit: did you know Pikachu has a higher attack score than special attack score? A physically based mixed set, with GK to catch physical walls, may be viable.
/endrant
But I'll get over my Pika love: while this is certainly an upgrade, it's still a gimmick.