If any Iraqi units put up a fight, it will be Saddam’s personal bodyguard, also known as the Special Republican Guards Baghdad Division. (In Third World nations, long unit names usually means short troop quality. Anyway.)
The problem with city fighting is that too many people die. Too many civilians — either too stupid or scared to leave, or used as human shields by their leaders — too many of your own soldiers, and it’s too hard to surround the bad guys so that you don’t have to kill them.
But we’re working on it.
NOTE: Did I say “bad guys?” Sorry if I offended any tender sensibilities.