Go for it. The flashing process is perfectly smooth and painless, just take a backup of the phone immediately before doing it and you can be back up and fully running on your new firmware in under 10 minutes.
When I flashed mine from UK to Global firmware the flash itself took 2-3 minutes, then started the phone and it spent approximately 5 minutes restoring everything and redownloading all my applications. Once that's complete, your device is in exactly the same state as before you flashed it, except using the global (and updated) firmware.