This is an old post but I thought I'd add some information to further the discussion.
Some years ago, when we added a room onto onto the house we lived in at the time, I discovered that the fancy thermostats for electric baseboard heaters were much more expensive and nowhere near as sophisticated as those for furnace systems. What I did find though, in the fine print in the catalog, was an accessory relay with its own transformer that allowed you to used the same thermostats you'd use on a furnace to control electric baseboard heaters. This allowed us to use a mass produced, reasonably priced programmable thermostat on our electric baseboard heater. Consider installing this relay yourself so you can use the wide range of existing X10 furnace control equipment on your electric baseboard heater.
I don't know if they mention this possibility anywhere in their documentation but this is probably why X10 doesn't make a special electric baseboard thermostat or controller.
