I Use these flashes for some time now. The're cheap, manual and powerful - in reverse order. I've missed option to control output power remotely - but solution is here - and in the way you'll love. Plus as simple as using YN-560III flashes.
It's a toy to set it, change any parameter and it never failed in any of my working conditions. I had wireless trigger RF603 before - worked fine all it's life. Now it's updated by YN560TX.