We added one of these to our hall bath three years ago.  When we remolded our Master Bath last year, we made sure to wire the toilet room with the necessary outlet so that we could enjoy a heated seat in there as well.
I can honestly say that there has never been an instance where a guest has used one of our bathrooms without first mentioning being surprised and then praising how comfortable that the heated seat was. 
We have been so spoiled that it is a rude awakening when we travel and are forced to use a toilet without a Heated Seat.
We highly recommend.  It is easy to install and we did not notice any addition to our electric bill.