We see these browsers, but the optimized versions seem to get no attention. For Firefox, it would be nice to also have a look into Waterfox and Palemoon. It would also be nice to see the TOR version of Firefox, but that's undoubtedly a lot slower.
There's probably even more Firefox derivatives. On Ubuntu there's Minefield and many more.
I use Comodo Dragon instead of Chrome and woulds like to see those two compared too. I'm not sure about it being faster, but it claims to be even more secure and it gives me somewhat more control over the browser. Importantly, it still works with Chrome apps
I don't know of a modified Opera or safari, but there's probably many browsers similar to IE. The only one I remember is MiniBrowser, but there are more.
Otherwise, it's a great article, except for the several typos. There were just too many! I stopped counting after three. Understandably, this is a large article so it has more chances for a typo to slip by proof-reading, but some of them were very inconveniently placed and I had to infer what they were supposed to be.