Running IOSU-level puts you at a level above even the vwii's boot chain, you could think of it as a sort of bootmii-level hax for vwii in that way. Not only can you install hax from cafe-side, you can also run games under the eshop rerelease IOSes (we refer to these as 'eWii') and play wii-mode stuff with gamepad controls. Running at a higher clock is likely possible too, at the very least IOP-side (faster i/o, maybe less latency on inputs).