I have analyzed MGT's analysis and found it not totally lacking merit.
EVERY Civ game has rewarded a turtle strategy followed by a breakout, rinsed and repeated. Civ4, with its emphasized SOD was the least rewarding to this strategy, as one simply kept up a constant rush, but as MGT states, the balance between building and expanding has been somewhat restored and one must now build up superiority to overwhelm defences, or suffer crippling losses.
I'm not as completely certain of the scout theory, but in many games of this type, it is more important to have any unit in a space than the quality of the unit, as long as that unit is not overwhelmed by a single attack. In other words, the scout is there to keep the enemy off the ranged units, not to do any damage. However, IF the scout is not upgradeable (I don't think it is), then the loss of production in creating a dead end unit is (possibly) not worth it.
Also, it seems infantry whilst good on the defense, as MGT states, will suffer losses on the way in against ranged. It might be better to execute a mobile defence so that the defending units can be used to attack with, when coming out of the turtle, rather than having to build an entirely new attacking force. I'm not sure how MGT plans to expand his shell, with only scouts and ranged to attack with?