We still actually use it in some of our production code, a toolkit for historical monitoring of various server performance and configuration details.
It was very handy for us since it was quite easy to put together some VBScript files under the control of Scheduled Tasks which did the data collection and transmission. This makes it runnable on a wide variety of Windows boxes without having to worry about compiling to the right target. It also allowed very fast bug fixing in the field since we can just ship a simple text file.
The fact that the source code is viewable is of no concern to us, it's not as if the idea of using WMI to collect data is some sort of precious IP :-)
I'm sure there's better tools but this was the simplest way we found. As far as I'm aware, it's still supported, inasmuch as they're still providing it in the later operating systems.
The only thing that burnt us (once) was the subtle changes between releases, such as objects themselves being deprecated or removed, making the WMI queries useless. We just need to watch out for that happening and adjust the scripts as necessary.