I had a gun slinging run yesterday that found a QC on -2 and decided to switch tactics. I turned it on, plugged in a particle charger, turned a HERF cannon and, and switched to a Nova cannon when fighting programmers. Those aren't even the best cannons, as zxc alluded to, and I was killing most enemies before they could fight back. I didn't even find heat to be a problem, my problem was draining energy too fast. I think a build dedicated around the QC needs either 3 power sources, or at least a good energy well or power amplifier. The QC is an amazing item.
I hadn't planned on going QC that run so I had 5 gun slots that became basically useless. It made me want to try a build where you never go bast 2 weapon slots, focus on cannons, and have all the extra support slots to support the QC (or perhaps even hybrid hacking). Anyone have experience with a non-melee combat build that never upgraded weapons slots?