If it is your own house and you are planning on living there a good long while, I would say it is worth it. I lived in a gorgeous house with heated marble floors for over a year and it was a nice treat in the winter. Just make sure it is installed right as the heated flooring in the master bathroom didn't seem to spread evely but I had no problems with mine.
The apartment I am in now has underfloor heating for the whole unit pretty much and it's great because it saves us a ton on our heating bill and keeps the apartment toasty and warm throughout the colder months. Sometimes too warm even