The SVOX US female voice isn't bad, but the male voice is horrible! On my KK I like the male voice. I've not tried Ivona. Might have to look into that.
I've gotten used to the TTS voices. When I listen to a real audio recording the inflection sounds strange to me. LOL
I use it on my commute to and from work with my Kindle Keyboard. The Paperwhite stays home - and it's all I've been using at home.