I'm almost sold on GV but I'm sticking with YouMail until GV allows me to upload my greeting messages as audio files. PhoneFusion allows this too. It amazes me that GV doesn't. Cell phones make horrible recorders.
I ported over a few of my audio files from YouMail by using Skype. It's a PITA workaround, but it can be done. Basically, you set the microphone in Skype to pick up the audio out of your computer. When GV calls your Skype line to let you record your message, you play back the audio file.
Can't find the website off-hand, but there's a few places with directions on how to do this if you search. Again, not the easiest, but I prefer all the other features GV offered over YouMail, so it was worth it to spend the time and do it.