My Sigma EF-530 has done a good job. The only 2 things I don't like about it are related. Being pretty powerful, it runs through batteries fast, and the battery door has a habit of popping completely off when changing batteries, though it only seems to happen when it is completely dark (Murphy's law at work?). Which makes for a fun few minutes of trying to not lose any batteries or the door, or break anything while attempting to reinsert the ears of the door into their retaining slots, especially since this tends to happen while shooting some action event where taking time to fiddle with it on the move is less than fun. If the unit had an actual hinge on the door, the problem wouldn't exist.
Tamron 70-200 SP AF DI-LD 77mm, Tamron 70-300 58mm, Minolta AF 50, Minolta AF 100 55mm, Sigma 20-70 52mm, Tamron 200-400 77mm, Tamron 28-300 XR DI-LD 62mm, Tamron 28-80 58mm, Minolta AF 70-210 55mm, Tamron 1.4 teleconverter, Sony 75-300 55mm, Sony 18-70 55mm, Sigma EF 530 flash, Canon S3.