The shots look almost like they have been scanned with a lazer LOL, their that clean sharp accurate in every way, above all amazingly natural looking especially with colour.
The back grounds from this lens seem first class based on samples shown here. The extra length would add compression over say a 50mm.
I think renting one for a week would be awesome, after all its a specialized tool, the purpose of renting is to determine a fit for enough application, the lens performance and quality is a given.
I prefer these days in times of chnage especially to rent more tools and own less, especially when you can add the rental into a price your quoting and the cost is tax deductible.
I feel from my early understanding that even longer focal length combined with 1.2, 1.4, 1.8 aperture will simply add even more benefits but how far is to far or to shallow.
Will Ai let us add the subject onto a chosen background more easily than ever before if things keep going the way they are, will higher resolution sensors and higher quality glass ie: like this 135 be needed to achieve these possibilities, who knows ?
Its interesting that even today the 200 F2 DSLR lens is still beyond words for what it is, i find my 300 2.8 VR II DSLR lens is arguably so close to the 200 F2 in many cases.
With these standard lenses unless used at F2 or F2.8 equally with the 135 at F1.8 there a waste of time, you may as well use a 70-200.
If doing model shots out doors with good natural lighting, i find the 300 F2.8 VR II at F 2.8 is highly capable and melts the back grounds out spectacularly well.
I see the 135 has dropped $1000 AUD here in the Grey arena.
I feel it seems based on all the discussion its a spectacular lens.
Fair to assume, if you have the room the 135 should be better than the 50 or 85mm focal length due to the 135 being able to compress things more, compression being very desirable.
Only an opinion