Hi,
I found it very useful to do health check or verify existing WLAN infra, as it will tell you various info on used channels, signal strength, noise level, problems, identify total APs, rouge AP, decode of packet, client details, alarm, pinpoint performance bottleneck and so on.
You can also use it for Site Survey for WLAN deployment planning as you can have more accurate info on the AP placement (how good the signal, noise, etc).
The only thing is, it might cost you a bit if you don't really need it. Useful for wireless vendor or customer with large WLAN deployment.
But this might not the case if you already have Cisco WLAN Controller in your larger and properly planned WLAN infra. WiSM will be extra bonus.
Rgds,
AK
