I actually like playing over my bass rig while playing Rocksmith, I hook up the realtone cable to my amp via the fx send output. So this way there is no problem with latency :) I play a TC Electronics Rebelhead 450, with an Eden 2x10XST cabinet and a homebuild Greenboy fearful 12/6 cab
I just started to do backup vocals in my band (I play bass) but timing can be a bitch when playing and trying to sing at the same time. While practicing I try to master my bass part first and try the vocals separately then try to combine the two, play it slower to get the right feel. Although for some parts I need to simplify the bass part a bit...