I happily throw Iphicrateans up against anything. They are valuable in phalanx mode but are just as good out of it. It's why I prefer them over the Macedonian phalanx. They can be out flanked and keep fighting and slaughter most enemies as assault troops as long as you don't throw them up against the very best. Plus since they are available as mercenaries any faction can have them. Of course the heavier version is far better and will keep fighting till the unit is almost completely destroyed. They are by far the most flexible infantry unit in the game.