Re: High kicking
Some possibly irrelevant insights from someone who has trained in Capoeira:
The secret to effective kicks is the same as the secret to... well, pretty much anything in Aikido, and most other martial arts: use the hip, not the limb.
Throwing a wild, high, fully-invested kick with the back leg is essentially the same thing as a haymaker: suicidal, but effective on the rare chance that it actually connects. Someone who is trained properly in kicking will generally either show the high kick as a precursor to a more effective technique or, as Amir said, will control the situation enough so that the kick is much more effective. For instance, Capoeiristas will feint and move in order to provoke a certain reaction from the opponent (think atemi), and then throw/show a kick once the opponent is committed to moving into the most vulnerable position relative to that kick.
In any event, don't ever let anyone tell you that a kick in and of itself is not an effective technique. In fact, my training with using my hips to kick effectively helped me considerably when I started training in Aikido. The same principles of moving from the center and creating power with your whole body rather than a single muscle or limb apply in both situations.