Have you seen the duet splice videos? https://www.youtube.com/watch?v=TUBva9_MlRI I really disliked Floor's voice on her own, but seeing them side by side...eh...it's not as bad as I originally thought. Tarja's still more heavenly, and less yell-y, but they're both good. Also found this one too...an ACTUAL duet with Floor and Tarja...holy crap! It almost brought me to tears https://www.youtube.com/watch?v=57WsNYItbSU
Yes, Floor and Tarja performed together in 2013 at the Metal Female Voices Festival. I think it was a great way for Tarja to "pass the torch" to Floor and for both to make a united stand and show the fans that there doesn't need to be this divide over the Nightwish singers.