Telmo:

TVN is the term that is use for Yamaha Custom Voice = sample with a special format.

Donny:

I prefer to embellish the board I got(now the T2, soon the T3), and make the best of what it can be.

I have observed that perhaps, that is why you change so often of keyboards.
You know, we are always saying " I wish this would have this kind of sounds, styles, features, keys, etc."

So, we already know that there is not "PERFECT" arranger by any brand or model for X or Y reason, and when a board is kind of "close" to what we like and or suit our particular needs for the type of style we play/perform, is good to have the possibility to make it even closer of what we want, in my case, adding the sounds I think I like better than the stock to use it for MY particular taste and needs, Roland also have the options to add boards with sounds, Korg to import them, and so on .
I see this as a plus, if it was not, no manufacturer would consider include them into their keyboards.