The area discussed is definitely worth visiting! If the offered hike to the signal de Botrange is not demanding enough for you, you should expand the walk to the open areas of teh hautes fagnes (high moors). There are easily enough paths to be found to get lost for a day or so. By the way the nice-weather foto posted is an exception, rainfull averages the low side of one and a half meters a year. This should not deter you however, the open lands of the hautes fagnes are even more impressive with gloomy mists or dark rain clouds hanging over them. Just bring your rain gear.
This info on the Hautes Fagnes has now been included. Everybody should walk in the rain at least once in their life!