Kellan Lutz talked about Rob on one of his recent interviews:

[THIS TRANSCRIPTION WAS MADE BY PATTINSON-ONLINE]
Girl: Can I ask you a question?
Kellan: Yeah?
Girl: How’s Rob–Rob Pattinson? His life?
Kellan: What do you think it is? He is one of the coolest guys I’ve ever gotten to work with. He’s super talented. I mean, his voice, his acting, his singing–like when I heard his first song on the soundtrack I was just blown away. It’s so–
Girls: Which song? “Let Me Sign”? “Never Think?”
Kellan: What’s the one where you can barely hear the words?
Girls: “Let Me Sign”
Kellan: I think that’s the one, and I just like–’cause I could barely understand what he was saying because of the emotion in it is so amazing. He’s so talented and to be able to work with him–he’s such an amazing actor, such an amazing guy–
Girl: I’m going to faint.

CREDITS TO PATTINSON-ONLINE