OK, you don't know what VVM is, not your fault, the name is confusing. Visual Voice Mail isn't video messages from the other person. Visual voicemail means the messages are downloaded individually and you could SEE before listening to them who they are from, as well as listen to them out of order, not as they came in. This app does not slow down my phone. I am running a stock HTC kernel (as the kernel source code for .207, .210, or .211 have been released for obvious reason). I don't use the voice to text... if I wanted to do that, google voice is free and does it OK, not great, but I can generally get the gist of any message.
Visual Voicemail Wiki