The FUJINON MK 50-135mm T/2.9 is a great all-round lens. It offers good optical quality and has a lightweight design and an affordable price for a cine zoom lens. For the entry-level filmmaker it will not be cheap, but in the context of cine zoom lenses there’s certainly nothing comparable right now. I would certainly recommend this lens, together with its little brother the MK 18-55mm. It’s a very good kit for documentary-style shooters, and currently there are not many other options out there that give you the same kind of video features on Sony cameras like the FS7, FS5 or even the Sony a6500.
Newsshooter seems to be less excited about the new lens:
While there is nothing optically wrong with the lenses at all I personally found that they lacked any sort of character. This is not a slant against the Fujinons, as there are plenty of other lenses on the market these days that have a very similar look to the MK zooms. The zooms do seem to pretty closely match a lot more expense Fujinon offerings such as the Cabrio and XK series. This makes the MK zooms a good choice to use on smaller B-cameras that you may want to match with a larger cinema camera running a Cabrio or XK series zoom.
Here is the Cinema5D video review: