

All the others have just been ways to fix various exploits. The only update Nintendo has done in the past 2 and a half years that has actually benefitted users was v4.0, which added the SD support (as crude as it was). Deletes (again!) the Homebrew Channel and BootMii(/IOS), and patches IOS exploits used to install them. v4.2 J- Second attempt at blocking Bannerbomb.(There's a reason they tell you not to reflash your BIOS if you don't really need to.)

Forced a bootloader update (boot2v4) that didn't actually fix any bugs or exploits - it just overwrote your bootloader "just in case" you had modified it, and caused a fair bit of collateral damage which Nintendo tried to blame on "hacking", even on virgin consoles. Added code to check to see if a console had its region altered, in some cases forcing a brick (!). Also added code to delete the Homebrew Channel and DVDX.

Any update that claims "behind the scenes updates" or "system improvements" refers to IOS updates, most of which are to patch exploits and very few of which actually impact performance, despite their claims. IOS fixes can never add functionality by themselves, they can only work around some bugs in disc-based games. Note that there's no technical need to update the System Menu, any version of IOS (the invisible "firmware" that implements all of the interesting security features of the system), or any channel at the same time. Let's consider the timeline of updates to the Wii software since the first exploit was demonstrated. This update is the first anti-piracy-only Wii update that doesn't add new functionality (or fix other problems). As for adding new functionality, Nintendo has been adding new functionality to the Wii from time to time as well (dare I say more than Sony has done with PS3).
