No big reason except maybe having to restore a number of my wallets, but I will soon do that.
You shouldn't need to restore anything... if you run the installer for 4.0.3, it'll just overwrite the old version of Electrum, but it won't remove/modify any wallet files and you'll be able to see all your existing wallets without needing to do anything.
Wallets are stored in the datadir (on windows: %AppData%\Electrum)... the application binaries are stored in C:\Program Files\Electrum... It's the binaries that are modified when you update, the datadir is unchanged!