Seems like a trend nowadays to have multiple vocalists and styles, be it good ones or unlistenable ones.
Sirenia (Female Clean, Male Clean/Grunt, Choir)
Amaranthe (Female Clean, Male Clean, Screamer)
Epica (Female Operatic, Male Clean/Grunt)
Solution .45 (Male Clean, Grunt)
Ayreon (Every vocalist and style imaginable)
All Ends (Two female clean voices)
To name a small few.