Well, if we are through discussing... errr...'team gymnastics', maybe we could discuss facing?
I think flanking is a very well designed rule, but I don't think that it is perfect. However, I don't think that bringing back facing is necessarily a good idea either.
The problem with facing is that D&D is turn based. That means that everyone except the character whose turn it is is largely frozen and unable to react, and that makes an absolute facing rather unrealistic.
Take a game like Battletech. In turn based pen and paper Btech, a highly mobile opponent like a VTOL can always arrange to attack the rear hex of a foe, and generally always after that opponent has chosen a facing. This allows a VTOL to pit its front armor against the rear armor of its foe, and generally only the opponents rear firing weapons. But if you try to do this in a real time simulation, you'll find that its impossible because the opponent will be reacting to your movement continiously. What this means is that 'facing' in a turn based game isn't actually realistic. The more abstract implementation is actually more realistic given the other abstractions that we've chosen.
So 'flanking' is in my opinion a better implementation than 'facing', both in being more realistic AND simplier and cleaner play.
However, it's not perfect. There are some issues that I would like to see cleared up, and they are in large part the result of another abstraction - the passive nature of AC.
Under the rules, the following situation:
XAX
XDA
AXX
Where 'A' is an attacker, 'D' is the defender, and 'X' is an unoccupied space, and similar variants of the above don't constitute a particularly serious situation. They are really no worse than this:
AXX
ADX
AXX
But realisticly speaking, the situation of being surrounded to the point that there is no where to turn where you do not present your undefended back is not only much worse than having all attackers to one side of you, but it is much worse even than being 'flanked'. It would be nice if the rules accounted not only for this but perhaps even for the fact that you can't defend equally well against multiple attackers as you do against a single one even if you aren't flanked.