It sort of seems skipped over now, but I'm a HUGE Paul Rodgers fan, and based on the two live shows they released, he sang the crap out of those songs.
I'm really not sure why it's skipped over. Everyone always goes on about how it's so different and how they could never get used to it. I didn't hear that much of a dramatic difference, when you're at a Queen show and someone's up there singing Queen songs really well, it tracks. And the dude saaaang. Obviously less versatile in style and range than Freddie, but it checked out. I didn't mind hearing the songs they did together (it was the part of the tour after they put out The Cosmos Rocks), and the BC/Free songs I already knew and loved. It was great, though of course my favorite bit was the Brian/Roger singing block with Love Of My Life, '39 and I'm In Love With My Car, because they stayed in front of us all the time (my sister, my brother and I were right in front of that little runway stage bit).
And then, when they stopped playing with him and started playing with Adam, everyone went back to requesting them to get with a rock singer instead. Why weren't they there when Queen played with a rock singer? Moreover, why would Queen go to a Jeff Scot Soto kinda guy next, when they just did tours with a rock legend, someone they actually looked up to when they were both starting out? It was time to go into a different direction.