Not a fan. And if it was just a matter of flavor wouldn't even worry about it too much. The real issue is that "origin stories" are spectacularly wasteful. Every additional companion costs a buckload more to be added to the game, forces the dev to give LESS companions in general and I could see a lot of these resources (money, above all) being better directed at aspects that would improve core mechanics and the experience for everyone (i.e. that infamous day/night cycle that Larian dismissed months ago as too much work to bother with).
I also confess to struggle a bit to see the appeal. I love experiencing these companions stories from a... well, companion perspective, but not even once playing BG1 or BG2 I've ever caught myself thinking "Man, if only I was offered the chance to play the entire story as Minsc or Viconia". Nah, that never happened.