You don't need any of these kits to crack wep and WPa passwords,
there used to be a linux distro called "backtrack" (BT3) loaded with apps for network snooping.
But nowadays even on a basic Ubuntu install can you find the aircrack and other snooping aps!
Why pay 24, when you can have it working for free on your wireless computer?
(granted that the kit might be a little easier to handle).
besides I read that cracking WPA passwords could take several hours to several days, depending on the intensity of the password!
Best thing to do now is encrypt networks with WPA2 passwords, generated by the computer, and stored on a flash drive.
These pwds are very long and difficult to crack!
But even then, it's a very simple task for a network admin to grant access to the wireless router to a few mac addresses, making it impossible for a leek who does not know how to modify his reported mac address to snoop on the internet.
The kit does not provide you with that ability. You'll need BT3 for that!