Utekineir, what SLR system are you bought into?
I have a Sigma EF-500 DG Super. It is supposed to be just as good as the higher end Canon flashes.. and it was, until it stopped working. It has completely stopped metering, or listening to the cameras metering, something like that. All my shots are now pitch black. I'm kind of pissed about it.
Used the flash with most of my lenses, all with great success. A good, powerful flash + diffuser is a really amazing thing. It is pretty shocking how much it can improve your shots.