I bought mine from Reddotphoto and PT-04-II, and have since served me very well I'd say (my 40D+EX580-I - not II ver. which I had sold away my entire 40D, etc...after very good "feeling/experience" with Oly E-PL1+m14-42+40-150+MMF2+FL36R, thus decided to sell and SOLD) with Nissin Di466 flash(canon-based-hotshoe), except that there ain't any TTL...
I have used the same on Canon 580EXII and it works. Just that it does not support ETTL hence manual adjustment of output power is required.
Another shortcoming is that the trigger unit is using a 12v batt. Sorry can't remember the battary model, but it is an uncommon type that I am still struggling to find