J. Larry, no problem reading the white print above the buttons on a black background, but keep in mind that my console lights the entire top of the keyboard with a soft, white light so that's not a problem.
For me, the vocal voices in the T4 are more gimmicky than useful during live performances, but I guess if they're used sparingly they could provide some pizazz to a few songs during a performance.
I just began working with the mic/vocal harmony section of the S-950, and I sincerely believe with some tuning, those harmonies could be pretty darned good sounding. I'm not convinced they will be as good as the TC Helicon Harmony-M, but if properly used, they could end up being a close second.
Someone posted something about the lack of a brightness and contrast control for the display - there is none on the S-950, but this particular type of display really doesn't require one. However, if you are sitting lower than normal in a chair and playing, they you may have some difficulty seeing the tabs on secondary screens. Other than that, the display is quite brilliant, far better than anything Yamaha has utilized in the past.
One of the things I've noticed is they have a VU-meter on the left side of the main screen display for the mic, something that I really like. You know immediately if you are over-driving, or under-driving your vocals, which is really important when trying to achieve a good balance between the vocals and accompaniment.
I just tried out the onboard audio recorder a few minutes ago and recorded a song that is really popular down in Don Mason's and Paul's part of the world - Amarillo In The Morning. I only spent a brief period of time with the mic/vocal harmony page, and this is just a one-shot recording, no different as if I were on stage. No backing tracks, no special effects other than some reverb on the mic settings - that's it.
Gary
Amarillo In The Morning