EXACTLY how does System.DirectoryServices.ActiveDirectory.Domain.FindDomainController() work?

I have a few questions about FindDomainController()

1. How does its functionality compare to the Win32 API DsGetDcName()
2. How stable are the results. The documentation for the version with no arguments states: "There is no guarantee that the same domain controller will be found by another call to this method.", but the other variants don't make this statement.
3. With regards to scalability, it is safe/advisable to cache the result from this method, or is there some internal cache inspection going on, and we should call it every time.

Many thanks

John