My short weekend with this lens is unfortunately over…

So a quick review was in order. Not that I'm a pro, far from it.
Physical.
It's a nice chunky lens to hold – there is a lot of glass in there and it shows, just holding it up to the light without any caps was a pleasure. There is virtually no protection on the body end of the lens where the glass is virtually flush so that’s something to watch out for. Also for some reason I had it in my head it was an 82mm filter thread but it turned out to be 72mm. Not that it mattered as I only had 77mm filters. The lens although technically not really heavy I found to be heavier as I was holding the whole camera by the grip more rather than under the lens/body. The lens however is nicely curved so you can grip it well from underneath. The other feature I loved was the snap-on/snap-off hood. Why can't all Canon L hood's be this simple! I hate the hood on my 70-200 with a passion. The focus ring is very smooth and light and very easy to micro adjust probably thanks to the epically long travel.
Focus
Yes this lens is slow to focus. The time it takes to go from the MFD 0.95m to Infinity is about 1.5sec. This will never be mistaken for a sports lens though with the 85mm focal length and 1.2 aperture it begs to be used for sports or indoor action. I did not particularly like the electronic manual 'focus-by-wire'. The body has to be ON for manual focus to work but in the end I stuck to AF.
Overall though once I understood how the focus worked I didn’t find it too difficult to adapt to the slow focus speed and found I was getting a good hit rate and compensating by overshooting. I even used the lens to grab some action shots of Eagles in flight using AI Servo with good results (albeit a bit of CA fringing)
Image Quality and how I did
Well you don’t really need me to tell you the image quality is superb – but I would like to say that even in the hands of a firm amateur like myself I got some really really great shots.
I hired the lens to use for my daughters 3rd Birthday party which was supposed to be a garden party but we got rained inside for half the day. We also took the kids out to Warwick Castle on the Friday and I packed ONLY the 85mm to take along.
What I had to understand with this lens is the extremely shallow DoF you get. Now you have to understand that my walk around lens is the 24-105L f/4 so I'm used to shooting at f4 or smaller apertures. I have a 70-200 f/2.8 IS too which is superb but not really my walkabout lens.
So going from an f/4 lens to a f/1.2 lens caused some major on the job re-training for me as I now had the choice of an extra 9 stops to deal with (1.2, 1.4, 1.8, 2.0, 2.2, 2.5, 2.8, 3.2, 3.5). I'm sure I didn’t get it right most of the time and I shot at f/1.2 probably more than I should have but hey it was fun to play.
The trick was getting the shooting distance up so the DoF was more controllable – however for the best bokeh – and I really mean the BEST bokeh – its meant getting up close but I guess all you pros already know that.
Daylight shots were tricky and I had to dial down the exposure most of the time. Someone above suggested an ND filter and I believe that would have helped if I had one. What I didn't get to try was the 85mm along with my speedlight as the batteries died (major DOH! For a b'day party I know).
Anyway that’s enough rambling – bottom line is I agree with many that this is a Bokeh KING and a superb Canon portrait lens but I can't help thinking that this is very much a specialist lens. You need to treat it with care and above all skill to get the most out of it – and I wouldn't use this for general purpose as I did. Stick to great portraits, great bokeh and controlled circumstances and I think you'll never be disappointed.
Thank again to all the posters and comment – I appreciated your advice.