Yanza is a small system which allows to control x10 devices. It’s installed under MCE and adds functionality needed to manage your home appliances. Free version of Yanza allows to control 2 x10 devices only. Which is appropriate solution just for playing with automation not for real using.
The next issue is x10 protocol. It’s very old and insecure. So, probably it’s better to use Z-Wave, Insteon, ZigBee or some other modern protocol.
And finally, you need Microsoft MCE to work with Yanza. IMHO some Linux solution is more stable and cost effective. For example, BlueLava is a set of Perl scripts. You can use it to control any number of x10 devices. Moreover, it offers a web interface. So, you’ll able to do that from any place. BlueLava is open source application. You can customize it as you want.
I wouldn’t like to say that Yanza is not good or whatever. I’m sure that it gets its users. But personally, I don’t see any reason even try it. Because the offered features are too pure and you can use it with MCE only.