For Excel 2010, adding argument descriptions for your UDFs has become quite simple now we have a new argument we can use.
For the older versions however -since this whole method revolves around some trickery involving re-registering a function that resides within a system dll- I want to make sure I caution the casual user. This is not a thing to mess around with. I would not advise using this method to register a large number of UDFs, using just any random set of function names from the dll. Make sure you test this thoroughly before distributing it to other users.
The ones we used in the demo work flawlessly however and have not caused any problems with our systems in the last few years.
If you are in the situation that you might have multiple Excel add-ins using this technique, make sure the add-ins do not use the same functions.