In my point of view the value of IT architecture is twofold. I think that there is an intrinsic and a company specific value of IT architecture.
The intrinsic value of IT architecture is comparable to the value you get from cleaning up a room. While cleaning up a room prevents you from tripping over things and helps you finding them when needed an IT architecture helps you keeping or gaining the overview of your IT landscape and thereby enables you to make changes to some part without breaking others. You achieve this mainly by setting and adhering to standards.
The company specific value of IT architecture is similar to the value you would expect from a satellite navigation system in that both help you moving into the right direction. For this you would have to develop and then follow a set of IT architecture principles from your business and IT strategy. These would be the IT equivalents of your principal business decisions.
One way to combine these values would be to develop an IT roadmap that would document where you are and where you want to be regarding your IT and how to get there. If you had already developed such a roadmap earlier you might consider refreshing it due to the dynamic nature of today’s economy.