I'd usually agree with this for most yank reviewers but this guy never beats around the bush, most of his views are exactly like just you and me the consumer.
1. He says it isn't a TITAN killer which it isn't as it needs a massive percentage lead to be classed as a killer.
2. He says mantle needs to be successful to create competition.
I think most of us here can agree with those 2 main points he made.
No he's talking trash, it's this very usual thing of making something up completely, saying someone failed to achieve this made up thing, calling it disappointing.
One person(forget who) said the 290x will ridicule Titan IN Bf4 alone, and WITH Mantle, but in that video he says AMD has been bigging up the card as a Titan killer.... and it failed to be that. AMD has not, is not, and will not tout this card as a Titan killer, so he's talking out of his ass instantly.
so your first point is irrelevant, it's no different to me saying, Titan needed to be a 290x killer and it isn't so it sucks.
As for performance percentage, again no, it does't have to kill it on performance to be a killer card in comparison.
Titan £800, R9 290x £800 5% faster, meh, if the R9 290x is £400 and 10% faster it IS a Titan killer. Outside of millionaires and lottery winners, a card is made up of more than it's performance. Cost, noise, performance are the big three for most people. If it does spank Titan in those area's it would indeed be a Titan killer to most people, but considering AMD haven't and won't market it as a Titan killer, it's all pretty irrelevant.
Second point, Mantle needs to be successful to create competition? No, it doesn't, Mantle could get in zero games aside from BF4, R9 290x is still a card that is significantly smaller while generally faster than Titan. THat is competition enough, more performance with Mantle helps, but it isn't required in any way.