Howdy, Bryan. A few comments.
First, it's not all about _moi_. As with any mature language with multiple implementations, there is a committee, Ecma TC39. It has reps from all the bigs plus PayPal (Doug Crockford) and Yahoo!. We avoid design by committee, instead focusing on paving the cowpaths and in a few cases working with champions -- single innovators or RPG's "resonant dyads" _a la_ ken&dmr -- to do focused design. The best example in my view is the Proxy design by Mark Miller and Tom Van Cutsem, followed by Modules by Dave Herman and Sam Tobin-Hochstadt.
We have a few goals, including minimizing kernel semantics and extending syntax for usability only where we have experience and positive user-testing results (e.g., destructuring, let, generators, classes as prototypal sugar a la CoffeeScript).
In this light, we aren't dumping new semantics into ES6. If you count fairly, we are filling the big semantic gaps in ES5 (AKA JS as we know it). For instance, where is client-side synchronous "require" without the ES6 module system? No fair that Node's require is sync (against all sound doctrine!). Sync XHR is from the jank-devil, and we cannot do sync require as an API client side.
Second, as others have noted, V8 was stealth'ed for two years (I learned of it in 2006 but Google withheld, see https://brendaneich.com/2011/06/new-javascript-engine-module...) and then unleashed just as Apple and Mozilla got their JIT acts together. At the time some said V8 was 3x faster, but the actual ratio on stupid benchmarks was more like 1.3x at first.
V8 is an amazing piece of work, but it did not contribute to the language evolution that my "very brief history" slide diagrammed. It certainly contributed by being the fastest, but until after 2010, that was the extent of its influence, for several specific reasons.
For the first few years as open source, V8 foreswore diverging from JavaScriptCore (the first WebKit engine, Apple's fork of KJS from KHTML, which V8 in some ways forked WebKit to replace) on any new ES5 or ES6 proposals, to try to keep on (or get back on, in view of the fork) Apple's good side. Fat chance!
Even now, V8 still keeps prototyped ES6 implementations hidden behind a flag. I expect this flag to be lifted before ES6 is ratified.
Another thing that hurt: Google has moved V8 to Munich because the Aarhus team wanted to do Dart, Google explicitly chose to invest in Dart over JS, and the no-remote-teammates rule hurt. IMHO the Munich team is quite strong but only ~10 people. This limits its effectiveness compared to Chakra (~60 heads?) and even SpiderMonkey (~12, more with interns).
Finally, whoever thinks I disrespect V8 clearly does not listen to my talks. The video will be up, give it a view when it's live if you have time. There is no disrespect from me toward V8 or the team that built it. I do mention it favorably in all talks, including Strange Loop (if my memory serves).
Lars Bak did the Strange Loop first night closing keynote, which my insane schedule prevented me from attending. He and I have had no meetings since that one in 2006, although he met with some Mozilla colleagues in 2009. I bear no bad feelings, although Lars did tell a gratuitous whopper around 3:50 in this talk: http://www.youtube.com/watch?v=T2TJYBmDZHI (see my blog cited above for what happened with Mozilla being "offered" V8 in 2006 -- Google reneged). He is the best VM hacker I know of. (Mike Pall is another superhacker of note.)
I hope this sheds some light. I respect V8 while noting that, as with anything human, it and the technical/product/open-source/standards politics around it show some significant flaws. That is inevitable.
Mozilla has flaws too, but they tend to be different in kind. For example, we do open from the start and try to partner even against long odds (e.g., Tamarin/ES4). I'm not bragging, because I think that can be a mistake. I've learned from V8 and modified Mozilla strategies accordingly.
So, hats off to V8!