Not much to be happy about here. The "Living standard" ensures that independent browser implementation from scratch is impossible. Even not from scratch, see MS Edge.
Sounds like they have yet to implement the proverbial last 20% of features which is going to take 80% of development time.
> Well, it can render and interact with Gmail quite well. It’s pretty much perfect on a few sites we’ve targeted as focuses during development, but it struggles with many others.
Same as Microsoft's OOXML standard. There are independent implementations but not one is 100% compatible. Even if that complexity wasn't deliberate on MS's part, it's surely a welcome feature.
And AFAIK OOXML isn't currently evolving as much as this Open Web.