I'm with BT Infinity & my actual speeds are typically 45.5/9.5.
Well that was before replacing my Billion 7800N with the Asus RT-N66U.
My download speeds were unaffected but my uploads dropped by a meg.
Initially QoS was on (by default I think) so I turned that off but no change. The bandwidth available had been set as 44/9 - not quite sure how it got that btw.
I turned QoS back on - automatic mode - and upped the available bandwidth to 60/12 and my upload speed was back. Turn QoS off & still all good.
So it seems that the upload can be affected whether or not QoS is off or on by what it detemined was the available bandwidth.
I'm using the latest Merlin firmware - 184.108.40.206.270.24 .
LAN transfer speeds seem a bit low with this router compared to by Billion but that's something else to look at.