Firstly, they're not rocket science!
There are few surprises in the rules, it's a given that GW systems tend to be simple. This is not to say they are not sometimes elegant games. Epic Armageddon and Warmaster both show how they can be quite capable of writing rules. Mainly though these are an exercise in putting a new spin on tried and tested rules; with a view to selling lots of pretty (and pretty expensive) scenery.
Not that I needed to worry about that, a huge pile of foam board still awaits the modellers knife. Thanks to pilfering old placards from my last office when they threw them away. The table was set with a variety of terrain, some of which I'd knocked up the day before.
The rules specify a set up with no two buildings more than 6 inches apart. This allows for spaces and roads to naturally appear. Players then pick a number of specified 'Stratagems', little special rules to reflect nuances of urban conflict. The value of these will vary dependant on you army, I made two poor choices I think, booby traps, and a fortified building (which I then advanced out of! In the right circumstances these could be valuable, but they do create some oddities in play also. For example only the player with the plunging fire stratagem gains any particular advantage for firing down on the enemy from above?...
Orks, thousands of 'em. Actually for a 40K ork army this was a tiddler, we only played 1250 points each, which took as long as 1500-2000 points as a result of the terrain. Nevertheless I had around 90 Orks and a tank to play with. By contrast Chris' Blood Angels numbered around 25 infantry, two Dreadnoughts and 4 other vehicles.
Overall it was a cagey game, although the mission required our capturing the central building, the lack of fire avenues mean't the Blood Angels at least couldn't thin out my numbers and were holding back at first. He quickly lost his flanking land speeders, but otherwise was barely harmed by the Orks. My Warboss suffered the ignominy of being cut down by a squad of scouts.
Chris' Dreadnoughts seized the building towards the end of the game, my Ork Burna Boyz tried desparately to use their blowtorch burnas to cut them open, but to no avail. Although I wiped out one Marine squad, the Death Company arrived as reserves and as usual mopped up my Orks. At the end of the game Chris was the clear winner.
In summary, City Fight is what you make of it, but contains little in terms of rules one couldn't come up with by mutual agreement. It has been used as a spur by GW to develop new scenery and figures (Eldar Rangers redone, finally!); but that also means the book is largely just a fancy add for the self same items. As one would expect of Games Workshop.