The new launcher contains are several new functions and settings like game auto start. Also, if you got the game freshly, the launcher will check automatically if you have all requirements installed.
If you want to know which features and changes are done to the program, check the wiki article right here: Pokémon3D article about the launcher.
To get the new launcher, click the download tab of this game, it might not be authorized when this news gets authorized, so stay calm and check this page out: Pokemon3d.net
Note: It is important to update because we also switched to a new download server (that is much faster BTW) and the old launcher won't support the new updates!!!