The difficulty with urban camo is equal to that of finding one "natural camo" -- there is too much diversity of urban environments. The villages and cities of the Middle East appear to have much different colouring than those of North America. E.g., where many of our small towns are brick and wood, most of the buildings I saw on the Golan were concrete. As a result, we may need more than one urban pattern. There is also the matter of seasons - are we going to develop a winter urban uniform, a summer urban uniform, etc?
Given our limited resources, we need to focus on reducing the number of line items in the system, not adding to them. Think of the effect each new pattern has - it affects uniforms, web gear, helmet covers, rain gear, boots, gloves, etc. Each kit item has to be carried in a multitude of sizes. These have to be stocked all over the country. Extras of each size are needed to ensure that each soldier is fitted correctly. Spares are required. The result of adopting a new pattern is exponential growth in waste.
Finally, who the **** is going to carry all this kit - if we are fighting in a mixed urban/rural environment, are we going to be changing continuously from one pattern into the other as we advance over several hundered miles of countryside??
Since urban patterns might be of great appeal to police forces, they may be the source of a product if it is proved necessary. While most seem to wear black, research on camo could lead to the development of a more effective mix of colour, pattern and shading. Perhaps we can let the private sector take the lead on developing product for this immense market - and we can then see whether anything worthwhile can be gleaned from their efforts. Even then, it seems like it might be best suited for equipping small teams for specialist missions.
In short - we can spend our resources more effectively than by worrying about urban camo.