Everything. They're stiff, the wedge interface is very good, and they're Odyssey... What more could you want?
I guess if you care about the paint wearing off quickly from your feet rubbing the arms, that's bad. But I don't mind it.
Best cranks, seriously. Stop reading this and go buy them already! They're Odyssey so they're backed with a lifetime warranty for starters. Unlike 48 spline cranks, they will NEVER develop a wobble due to the splines wearing out, as they have no splines but a hexagonal wedge system instead which keeps everything nice & tight. Mine are nearly 3 years old and still feel as stiff as the day I bought them, and much stiffer than the 48 spline cranks I've ridden in the past. Get them!!