Your developers don't spend time trying to figure out what looks best
I try pretty hard to have the software that I create be as clean and professional looking as possible. In order to see what looks best though, I've spent a non-trivial amount of time trying out different combinations of form background colors, static text labels fonts and colors, field fonts and colors, section headings, table formats and so on. If each of your developers has to go though the process of deciding what looks and works the best, they're going to waste a fair amount of time. These kinds of decisions are also subjective.

Finally, if there are some special hardware or software considerations in your environment, developing standards to address them up front will answer a lot of questions from the developer community going forward. What kind of considerations am I speaking of? If your Notes applications are all going to be used on Macintosh computers or if your users' hardware always supports 1024X768 screen resolution, you might want to take advantage of that fact when designing your applications.

Applications developed by consultants and contractors for your firm have a formal guideline to follow
This means that your hired guns don't spend time (i.e., billable hours) trying out different font and color combinations. It also means that the applications that they write will look and feel like the rest of your internally developed applications. This should reduce training and support costs (as we discussed above).

With standards in place developers can more easily work on each other's code, reducing application maintenance costs
This one isn't so obvious but it really works out. Here at Tactica Technology Group, we have a formal design standard and it really makes going from project to project and application to application a lot easier. When I have to work on someone else's code, I know where to find things in the interface and I know how I need to make it look.

If your applications use a standard set of subforms, shared fields and views and folders, migration to R5 will be easier
Now that's helpful! At Tactica, we use 22 different Notes applications to run our business. Each of these applications uses the same design and interface components via subforms. As part of our R5 migration process, we needed to test these applications. We tested, validated and upgraded one set of standard subforms, views and folders in our standard design template. Once that was done, those components didn't have to be tested in all 22 of the applications.

What kind of things need to be formally defined in your UI standards?
If you've gotten this far in the article, you probably agree that UI standards are a good idea. Well, what's the next step?

You'll need to determine what parts of Notes UI design are up to your developers and what parts need a written standard. Since forms, views and navigators are where your users will spend most of their time working in their applications, you should be sure to pay the most attention to those sections of the standard.