First reviews are out (on preproduction models obviously) and it looks promising.
Half the weight of the Sony 70-200. Takes up half the physical space in the bag, since it extends (it takes after the Canon here). Sharper, particularly in the corners. Focuses just as quickly. Well-buult, still weather-sealed.
On the downside, no external buttons or switches (need to choose in-camera if you want to MF), feels less solid than the metal 70-200 (not that it necessarily is less solid - metal always feels more solid, so I'd look forward to a teardown by Lensrentals), less flare-resistant (not that flare is typically a huge issue with telephotos).
I'm definitely keeping an eye on it. I'd probably go for a 70-200 if it were my primary lens and used it day-in, day-out (e.g. if I shot weddings), but, for me, a 70-200/2.8 (or 70-180) would be infrequently used, but invaluable when needed - as a companion lens to a longer, slower 100-400, 200-600 or prime for low-light situations under the forest canopy, for the occasional portrait (180/2.8 does a perfectly good job of head-and-shoulders portraits and obviates the need to carry a separate portrait lens when you're already carrying this lens) and as an even lighter alternative to the 100-400 for hikes or excursions where I don't anticipate needing anything longer than 180mm.
Not that it's perfect - I'd definitely have appreciated a customisable button, an AF/MF switch and a focus limiter, which would add functionality while adding little to the weight. But, for half the weight, half the volume, half the price and a sharper lens than the Sony, it looks like a pretty good deal.
