I own both the Canon Rebel 2000 and the digial Rebel. I also own the 420EX speedlite. I am planning to purchase the ST-E2 transmitter. I know that the transmitter works with the 420EX but I am wondering if it might also be useful in firing other (non Canon) infrared flash units. It would be helpful, at times, to add small flash units to obtain light from different angles. Thanks for your input.