If you wanna upgrade, there's no downside to doing so.
Right now, you can do browserhax and then install themehax to get homebrew. You can do things like emulate old games, backup and restore save files on cartridges or digital downloads, and run romhacks for games like pokemon.
If you want CFW's, you're gonna have to wait. The exploits that will let you downgrade and get kernel access aren't available yet, but when they do release they will work on 10.3.