"Slot blowers" useful or not ?

[soulfringe]

Was curious if anyone knew just how useful slot blowers were.
such as http://www.jab-tech.com/Antec-Super-Cyclone-Blower-pr-2952.html

 

[leo2kp]

They can be useful to take out some hot air inside the case, but as far as getting rid of local hot spots like processor area, use your normal exhaust fan and don't let that CPU air circulate through the case.