ATT and AtiTool are actually overclocking apps, but in the case of ATiTrayTools, you can adjust AA,AF, monitor temps in graphs, show temps in overlay while yo play games and very important, set fan speed ratios's based on temps.
CCC, must have .Net installed. CCC is just a nice looking interface for setting errr... settings. But, alot of people get the driver only (ATi releases the driver/ccc in one package), and use ATT because you can create profiles which will load AAx4 and AFx8 for game x - this will automatically be done each time the executable is run. So, you rarely need to adjust the settings before launching the game, and it's faster than CCC's profile.
Not going the CCC route, might give you some hic ups with using ATi's transcoding though.