I don't mean much, but reading for various forums it reads this:
Hardware acceleration can be bad for gaming.
Hard to say if that is the cause or the symptom. Ex: People with higher speeds like CTF / Hardware acceleration. Higher speeds reduce the need for QOS, though they typically don't fully eliminate it.
If you enable hardware acceleration, you don't enable the same QOS. Stuff like Cake can't keep up with massively fast connections. Tomato QOS has never been accelerated. Only FlexQOS is available as a nice hybrid on these routers. In the past even 100mbit+QOS was too heavy for most router hardware, yet was still within reach of having buffers burst-filled suddenly by large spurts of data from YouTube, Netflix, torrents, Steam downloads, etc..
So you got a mix of people that wanted full internet speed (200mbit comcast, etc.) and didn't use QOS because it slowed their connection down - but then could suffer from BufferBloat and ping spikes in games (when other services start bursty downloads - or services like dropbox hog all the upstream) - and people that do use the (older, less effective) QOS types, get pretty good results, but have their overall maximum speed fall due to lack of acceleration. Especially when there's tons of connections, and the router CPU can't keep up. That explains the stories and conflicting viewpoints. Hardware acceleration is bad, QOS is bad, QOS isn't needed over a certain speed, QOS is still needed over a certain speed, etc.
That situation is pretty logical though when you look at the internet speeds, router hardware, services used and types of complaints.
Now-a-days you just throw more hardware at it, turn on acceleration, turn on FlexQOS. Done.
As long as you set your speed %'s low enough to allow UDP traffic some breathing room (many UDP protocols lack retransmit or throttle mechanisms and may not do well with latency volatility) then it should function as expected.