I have a kind of mixed response to this thing. When I had a chance to play around with one at AUSA last year, I was impressed by the volume of firepower you could put out in the short term, but also less than impressed by the size/weight of the thing, and the amount of time it would take to reload (no 40mm speed loaders like a .38 revolver).
Like everything else, there is a time and place for such a device, I would say it would be best employed in a defensive position or as part of a fighting patrol when you are setting up an ambush. Lugging it around in OBUA fighting is probably the last thing I would want to do, with advance to contact (section attacks) coming a close second.
In the Infantry board, Infanteer put up a series of posts about the infantry attack pointing to experiments done by the USMC. The Marines separated heavy weapons out of the rifle squads (sections in our terminology) and grouped them in a fire support squad per platoon. The heavy weapons in this case was the SAW (our C-9), and grouping them in a separate organization made the other squads faster and more flexible. The "ideal" ideal solution would be to have an "automatic rifle" to provide high volume fire in the squad/section (the Shrike LMG or Ultimax 100 are examples of what seemed to be sought), while support firepower is grouped together for volume of fire. This would include grenade launchers like the M-32, and machine guns like the C-9s and C-6's. If it were up to me, "shoot through" rifle grenades would provide the rifleman with the ability to reach out and touch someone without the added bulk of an M-203 or M-32, but that is my opinion.