I have the 430EX and ST-E2 but rarely use the flash off camera. It works fine though. If I was making the choice again, I'd go for the 580EX purely for the extra power. I only ever use the flash off camera for macro work and an off camera shoe cord is sufficient. I seldom do any portrait shooting so I can't really advise you on your specific needs.Two things to be aware of is that 1) the ST-E2 uses expensive non-rechargeable batteries and 2) while slaved to the ST-E2 the 430EX flash emits 1 per second pulses from the infra red AF assist lamp which you and your subjects might find distracting/irritating.