Developing my first App for Office (specifically Excel) was an experience I found to be unnecessarily difficult. The Trusted App Catalogs user interface in Excel:

File -> Options -> Trust Center -> Trust Center Settings... -> Trusted App Catalogs

Is a giant mess. There's no browse button - just a field to punch in a string that has to be formatted a specific way and only allows network shares and SharePoint remote servers. First off, I was expecting to see a checkbox to "Allow manifest files from untrusted locations" that would then open up a way to select a XML file via the standard Windows "File Open..." dialog within Apps for Office itself. The File Open... dialog handles all sorts of scenarios that are useful and flexible (e.g. it can download remote files via a URL). Excel shouldn't care where the XML file comes from after such a checkbox is checked. Then, if you really truly wanted to define an entire catalog, have a XML index file option where the XML file points at a bunch of other XML files. And while you are at it, add a button that allows a user to export their catalog to an index XML file in the appropriate format (i.e. allow a developer or other qualified IT employee at a company to construct the catalog and then export it). This allows you to get rid of the entire Trusted App Catalogs dialog altogether and have a sane Apps for Office dialog that actually makes sense. The way it is built now also basically stops local computer development of new apps (WTF?) unless the developer knows Windows intimately and can figure out the '\.\C:\path\to\manifest' hack that makes a local drive LOOK like a network share to the clearly poorly written code behind that dialog. When there are grammatically incorrect strings being emitted, you know the code is crap. Again, the dialog should not exist at all.

Having to restart Excel after making each change to the Trusted App Catalog dialog should have been the first indicator that perhaps the Office Platform team was going about Apps for Office all wrong.

I'm certain that if Bill Gates still worked at Microsoft and sat in on the meeting regarding this non-feature of the Office suite, the F-word counter would surpass whatever the existing record is. This is alpha-quality (at best). Go back and redo.