Why listen? Read your voicemails instead! Much faster.
Try a voice-to-text transcription service such as
www.dictomail.com or
www.phonewire.com
More info:
http://www.blackberryforums.com/showthread.php?t=315
Yes, you can still listen to your voicemails in the normal manner, but now you have the choice of reading your voicemails. Love the service. A bit expensive, but I love the service. (I'm a deaf guy, so this system is very useful)