Britney Spears -- Crowd ROARS After 1st 'X Factor' Critique

Britney Spears' first day as an 'X Factor' judge is NOT a total disaster ... in fact, the pop star has been articulate, encouraging and even funny at times.

Audio has emerged from the first round of auditions in Austin, TX ... where Britney has been dishing out criticism from the judge's table with Simon Cowell, L.A. Reid and Demi Lovato.

It didn't take long for Britney to clash with Demi ... they disagreed with each other on the very first contestant -- one person LOVED it ... the other, not so much.