I've heard about the HomeBrew stuff (wiki) that'll let me download and install simple games and even write my own, but is it fully compatible with the latest updates? I've heard horror stories of people bricking their Wii's.
I've softmodded my Wii to run HomeBrew software, and haven't updated the main Wii OS since, the changes are not that important, and if you wait for the new softmod to be avaibable for the new version, you can do it that way.
There is a very small chance of bricking, and the newer methods are very foolproof..
Regarding upgrading, Menu 4.2 :
In conclusion, just a bunch of checks to brick/restore your Wii if you are running softmods or homebrew additions.
And the next update 4.3:
So it only adds usb webcam support (IOS58) and more checks to brick/restore your Wii if softmods are detected.
So the last 2 major "upgrades" were just to brick/revert your wii if you were running a softmode/homebrew software, enough reason for me to stop updating the OS and enjoy the homebrew software.
I've softmodded my Wii, and it didn't brick. There is a risk, but if you are following instructions then you should be fine. There are no guarantees though.