I did a gig last Saturday night with a guy that uses Sonar X2 to sequence just about everything. Bass, drums, keyboards, and horns were all done using X2.
Most everything used Kontakt. He used Battery 3 for drums, various keyboards (piano and organs), and Session Horns for brass. For bass he used the Cakewalk Session Instruments Bass.
It was all controlled from a laptop running X2.
He also had a TC-Helicon unit he used for harmonies.
He used the lyric view to send the words and chords to the songs to a tablet mounted on my mic stand
He had a really good sound system and some killer monitors so it was all sounding great, like playing with an 8 or 9 piece band with a bunch of background singers.
Unfortunately I forgot to ask him what kind of interface he used to get everything from the laptop to his mixer (DOH!).
He said he would be calling me for some more gigs so I'll be sure and ask him then.
It was a very eye opening experience, I had never seen SONAR used in a live situation like that, it went without a hiccup.
I really enjoyed it.