Wanted to update this in case it helps others. I thought it was working fine on CM M9 and nightlies however it was only temporary. What would happen is that the pending voicemail notification would show up at some point and could never be cleared.
Googling around I found a lot of suggestions to:
>>
Go into the Visual Voicemail application and compose a Visual Voicemail message by selecting
Menu and then
Compose. Make sure your message is longer than 15 seconds and send to
activate@vvm.sprint.com.
>>
for various visual voicemail problems though not the pending problem.
ex
Troubleshoot if you are not receiving your Visual Voicemails
If that link isn't working here is the text, so you just perform step #4
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Troubleshoot if you are not receiving your Visual Voicemails
Last Updated: Sep 28, 2011
Try the toubleshooting steps below if you are not receiving your Visual Voicemail messages:
1 On your phone keypad, enter *38 and then press Talk to cancel any call forwarding
2 Turn off your phone, remove and reinsert the battery and then turn it back on
3 Update the data profile on your phone; go to Menu > Settings > System Updates > Update profile
4 Go into the Visual Voicemail application and compose a Visual Voicemail message by selecting Menu and then Compose. Make sure your message is longer than 15 seconds and send to
activate@vvm.sprint.com
>>
https://www.youtube.com/watch?feature=player_detailpage&v=vhfyQI5C2vs#t=18
After performing that, it worked for me. It seemes like initially after you do that, there can be a bit of kicking and screaming by the client but it does settle down and start working.
By kicking and screaming I mean I might get a few weird notifications / texts about downloading vms, or vms, but it seems to sort itself out quickly and start working.
using it successfully on M10 and the moment as well as some nightlies