I made these last night for a dinner with friends. They came out beautifully - they do make a nicer presentation than standard baked spuds and the lemon butter adds a very nice touch. They went very well with brasato al barolo.
Only caveat I'd put in is to be careful when making the partial cuts through the potatoes. I found it to be very easy to go a little too far and end up with two pieces of potato rather than a single fanned one. Be careful with this step and the rest is easy.
Thanks, Bill!
Mike