ummm...if the optics and AF are good enough, me.
Seriously, look at the
MTF charts...
If these are accurate, they are better at 600 mm than the 5
0A.
AF will be a big question mark. And I won't believe anything until I see some test results. But, this could be an excellent optic at 600 mm for $2k. If so I could easily be the market.