Any benefits of upgrading ?

I'm running my wii with wiikey2, software 3,4e downgraded on some levels to enable wad installing etc.. this is all about a year ago, and I haven't played really much with my wii on a long time.
Just been watching series and movies via mplayer_ce.
Now I bought two motionplusses, aiming to play some games.

Now I got wondering, is there any reason for me to upgrade my software ? Or any bits of it ? Thanks

Its good to goto 4.1 if only for preloder and running games from SD card.
Don't go to to 4.2, no advantages there, only problems.