Variety
One thing I have found during my personal adventures in cooling is that you can't make a blanket statement to cover every situation.
There is such a variety of cases out there that what is terrific for one might be awful for another.
The one constant I have found is that an intake fan on the side of the case blowing directly onto the CPU/Video Card area is a good idea, provided your exhaust fans are up to snuff.
My main rig is a full tower (generic) with gobs of places pre-drilled for installing fans. I went on a fan binge a few years back and at one point had 16 fans going! (This included two hard drive coolers which had 3 fans each, a bay cooler with 2 fans, as well as the chipset, cpu and ps fans, a slot cooler fan, twin exhaust fans on the back, an intake fan on the front, and the side fan blowing onto the cpu).
With the exception of the mandatory fans (cpu, etc) I found that the side fan did more good than all of the rest of them put together (and I tried many, many combinations).
Prof
PS: My side fan is a 120V 5" fan made by a German company - it really moves the air!)