I use it occassionaly. Usually its to manuever my cavalry quicker when they need to move laterally and such. The other time is for the "berserker" units, such as highlanders, gallowglasses, etc.. when I need to use them to bust up a unit of spearen. Wedges can absolutely ruin the formation of a spear unit, giving your otherwise cheap, throw away unit a quality chance against a more expensive unit. I did a test run of highlanders vs. feudal seargeant. If I kept the highlanders in their original formation, it was disaster, as the spearmen were able to keep formation. However, in wedge, their odds improved considerably, winning 3 out of 5 battles. Still not totally reliable, but considering cost and tech, it was a big improvement using the wedge.