Well, probably the first strategy would be to make sure there is plenty of terrain on the board. WE have to have trees, so if your opponent is playing on a board with lots of rocks and hills, or impassible terrain, you may not have anywhere to scout. The only advantages the waywatchers have over the regular scouts is the lethal shot (rarely comes into play), and the fact that they can scout within 10" if unseen. Yes their BS is better, but the scouts are quite a bit cheaper, so I think that's a wash.
Another major disadvantage of the scout/WW characters is their inability to take combat effective weapons. At some point, you're going to have to fight. You're going to get charged, if for no other reason, than to keep you from shooting. My main problem with these kind of lists, is that your guys shoot just as well from far away as they do up close. If there was some kind of killer unit that could get really close, then eveyone would take them (ie. alter nobles, wardancers with moonstone, etc) otherwise, the whole point of having ranged weapons, is to shoot them out of range of the enemy. I don't know if there is any strategy to this kind of list, because I don't think anyone plays it. The list on the website was intimating more towards a fast moving list with skirmishers wasn't it? Glade riders and waywatchers with forest spirits. That makes some sense, but why not use the other units. IF you want to scout a couple of units, get 2 small units of waywatchers instead of the eagle. Then get some gladeriders and wildriders and forest spirits to back them up. The problem with the list that GW proposes as the ambush list, is that you have nothing that can stand combat. This army can only kill other ambusher armies. None of the units can hit hard enough to make the enemy disappear. It could work in small point games, but in a large army list, it doesn't have a chance. Nothing is over str4 in the entire army. Most of the army is str3. Dryads are good, but they are generally horrible against ranked units. You're basically hoping for the opponent to line up his guys and you try to panic them all off the table. It's unrealistic. I would instead go for a faster moving army which hits hard. You have to have something that can smack teh opponent or burn through armor, otherwise there are several armies that will just eat you alive.
