Simply put, Wi-Spy is wireless LAN RF analysis for the rest of us, doing for wireless LAN RF analysis what NetStumbler and Kismet did for WLAN packet capture and display. Given the $2500 and up price points of every other available product, MetaGeek could have charged a lot more for Wi-Spy. But instead, they chose to be a breakthrough product, bringing real RF spectrum analysis within reach of everyone, not just Enterprise IT departments.
Sure, it doesn't have all the features of the higher-priced products, and for $100 you don't really expect it to. But MetaGeek seems to have made the right tradeoffs in Wi-Spy's design, with the result being a product that delivers not only what's needed, but some nice little extras, too.
Wi-Spy still has a few rough edges and I ran into a few error messages that were probably thrown by .Net, such as when I tried to bring up the Help menu after I had been running Wi-Spy for awhile. But if you've been lusting after the high-priced stuff for a cash-strapped IT department or just for hacking and exploration, then lust no more - just buy it!