Insteon is fast and reliable here, and the value is fantastic compared to competing protocols.
For not more than the price of a single device with another protocol, you can pick up a plug-in starter kit. For just $99 (free shipping, too, if you order from Home Depot online), you'll get two SignaLinc RF coupler/repeaters, a couple of lamp modules that can plug in anywhere, and a ControLinc. Since each device is a mesh network repeater, so if necessary you can move those LampLincs anywhere in the house you need to boost the network.
Obviously price isn't the only basis for your decision. Flexibility is great, since every device can be part of several scenes, each with different ramp rates and dim levels. Device response is instant, not delayed by a second like some systems. And since controllers, responders and couplers are all available as plug-in devices, you can experiment with the protocol to your heart's content without rewiring the house or calling in an electrician to wire in a coupler.
Tom