Been playing around with Iray a bit more, and it's been a frustrating experience. VRAM management is next to impossible, as the log file is really sparse, and the system seems to allocate extra VRAM "just in case" if you have it.
This means you can't really use external apps like GPU-Z for management, because you have no idea what the numbers actually reflect. I just upgraded from a 2 to a 6 gig card, and scenes that rendered fine in GPU before now takes up more than 2 gigs of VRAM.
It also seems that it loads every texture as RGB, so a bump map uses as much memory as a normal map.
But it's easy to use, free and most people on the DAZ boards have NO idea what's going on anyways (see the threads about optimizing for AMD performance). I think most are rendering in CPU and just like the pretty results