One process per tab is not a feature. It is (or should be) invisible for me, the user, and from my experience it creates more problems than it's worth (first time I tried Chrome it simply stopped my computer dead by running 10 heavy processes on a single-core CPU - so much for performance). It's a bad design decision that will only pay off when I have a 20-core CPU.
Sandboxing for individual tabs? Just about the same.
My point is that saying "Chrome came and shook things up introducing features no existing browsers had" is a bit of a stretch. When it came out Chrome was basically not very different from Internet Explorer 6 (feature-wise), and it seems to have stayed that way (I like full page translation but that's it).
We should be fair and say that Google Chrome has a large market share because it has Google behind it. It doesn't have much else going for it.