I do like the TTS feature on the Kindle and often use it when I'm in the middle of an exciting read but I have to go and prepare a meal or get on with housework. That way I can still continue with the story.
The male voice (Tom) is pretty good - much better than I was expecting.
But I wish I could have a voice in a British accent - just because it would be more comfortable to listen to. So yes there is a need (maybe a niche one) for other voices.