WiLMa is a utility for adjusting various settings like Mail servers, default printers and even desktop wallpaper based on which Location you're using (check your Apple menu if you're unfamiliar with the Location menu). WiLMa can even open and close applications and set a default network to join. If you're a nomad who bounces from places like work, school, home and who knows where else, this could be quite a handy utility, though it isn't without at least one disadvantage: it runs as an application, which means you need to have it in your dock if its corresponding menubar item will be accessible. Location X, by comparison, is more of a daemon that runs in the background, watching which Location you're using and automatically adjusting these settings to your preferences, without the need for an app to run in the dock.
Of course, with WiLMa's more attractive $12 price tag (Location X is $20), Universal Binary status and unique features, WiLMa definitely has a good thing going for it. A demo is available from Codehackers.