This review is very much a waste of time. It is more than a year after the the-digital-picture review for example and says less and gives less detail in more words. As for focal length, it says nothing about the performance with the 1.4x and 2xTCs, and doesn't even mention the latter. It says that one con is the weight, but it weighs far less than the 400, 500 and 600mm f/2.8 - f/4 primes and gives IQs not much worse than them with the TCs. The reviewer just doesn't realise that the high quality 300-600mm range in a relatively light package is what this lens is all about.
But I don't own a TC. I'd like to though
You can't have wasted *too* much of your time on it, though, since if you did you would have read my statement "That’s why I wrote this piece completely from my perspective, from the curious photographer, wondering if I need just a little more reach. " Which is obviously not your position. I've never used a 300mm lens or a greater focal length, neither have many others, so I wrote it the only way I could, which is from my perspective.
A waste of time for an accomplished, well seasoned photographer whose used every lens ever made? Yeah, absolutely.
Your constructive note about it weighing less than a 400, 500 or 600 is appreciated though. Unlike your opening statement, I found that point useful.
If that was the purpose of your writing, then you should not have called it a review but should have chosen a more appropriate title. As it was, you led the reader to expect far more than you delivered. If you called it "My first try with a 300mm lens", then I would not have complained. But the simple title "Review - " without any qualification raised anticipation to expect what wasn't there.