The debate seems to be fading.
Big bandwidth is simple and cheap.
The argument for QoS has always been that certain types of traffic, such as voice and video, need to get through a network in a timely manner. So those real-time packets should be given a higher priority than the rest of the data, to make sure they have access to the available bandwidth. The argument against QoS has been that if gobs of bandwidth are available, then prioritization isn't necessary. All packets will get the bandwidth they need. The latter argument makes the most sense in the LAN, as the prevalence of Gigabit Ethernet at rapidly falling prices is giving desktops and servers more bandwidth than they could possibly use.