They've got a slew of dealer accessories for these now... as you can tell in the pic, I've got the solo seat cover. That was worth the money, only 50 bucks, and it looks great.

I've also since bought the fender (big plastic plate holder thing) eliminator. It really makes the back of the bike look nice.

They've also got full fairing kits now, rear wheel huggers, and SV1000-like belly pans. The full fairing is something like $650, the belly pan is around $400. I think the hugger is a few hundred bucks.

As for performance, I know a full M4 Race exhaust system bumps performance from 70rwhp to 75, but I think its around $800 so thats a steep hill for 5 horsepower. I wouldn't even bother. "Slipon" mufflers are around 400 bucks, they sound awesome.