I am rooted so I renamed the 3 OGG files mentioned in this post via Root Explorer ..
That thread mentioned another app but I couldn't find it in the Market. Renaming those 3 files was a quick and simple solution.
---------- Post added at 09:13 PM ---------- Previous post was at 08:59 PM ----------
I tried the Voicemail only option (instead of full Google Voice integration) in Google Voice settings through the webpage settings. It forces all voicemail to one greeting. So I can't have one greeting for my business line (Google Voice #) and have another greeting for my personal line (Sprint Cell #).
However, I did notice that it will display voicemails in the call log with the ability to play the messages from the call log. With all this messing about I didn't have that but after trying Google Voice voicemail only integration and then disabling it with the code provided it seems to work from the call log now at least. I still prefer Sprint VVM, hopefully there will be a newer APK that will work in the near future.