I'm led to beleive the 430EX has a stand-by mode that can't be disengaged and after 'X' amount of time, it will power down and has to be manually (by hand) restarted. This is a pain if it's situated metres away, as you'll have to leave your shooting position every time.
Why not look at the 540EZ - it's basically a 550EX without the full digitial compatibility, plus it can be used on manual and it doesn't power down in the same way so is always ready to fire. Seen these going on ebay for about £60.