If you downgrade, you can use all homebrew plus all the features of higher firmwares (up to 2.71 at the moment) thanks to Dev Hook. You can also use Dev Hook to launch all 2.0+ games on your 1.5. Email me and I'll send you a link to Dev Hook with all the needed files.
Also, you can exit homebrew by hitting the HOME button with homebrew on 1.5, to answer your question.
Bookmarks