Hi, unfortunately it is not so simple.
We have discussed these issues time and time again in other threads, like this: viewtopic.php?f=20&t=15165
and we have tested under MacOSX, Windows 7 32, Windows 7 64 and Windows 8.
Under the same exact conditions, using the same exact source we have seen different behaviors. Sometimes it hangs, some other it doesn't. The problem is not with the API but it has to be found way down in the native code that is generated by Unity from the C# bytecode.
With the latest API and using the OnApplicationQuit trick we were able to remove the problem on all platforms we have tested, however there are still reports of problems even though we're not able to reproduce it, at the moment.
I proposed to submit a bug report to the Unity Team but so far we haven't got a reproducible case. If you have one you might go ahead and provide your sources to the Unity dev team to take a look.