- First of all the 1.8 is also sharp wide open
- I compared f1.2 <> f1.8 bokeh's and there was very little difference (I swiched many times screens between same pics, the 1.8 is dreamy enough!)
- they both have purple fringing/CA so no advantage of the L.
- f1.8 is mostly the edge to have both eyes sharp, f1.2 too thin if the head is not straight
- f1.8 is fast enough (and I also work with 5D2, so even ISO3200 is no problem)
- faster AF is always welcome
- lighter and more compact is nice
- I bought the L second hand for €1000 and sold it for €1000, so I actually borrowed it
- €750 extra in my wallet is always welcome (tabletpc or extra lens,...)
I thought of the MKII (too expensive and probably not worth the cost either) and Sigma 85 1.4 (if you are lucky that you have a good copy, but reviews say harder bokeh and less IQ).
So 85 1.8 seems the best option, I don't see it as a downgrade but a more comfortable lens.
@ Bianchi :
The reason I wouldn't sell my 35 1.4L is that it has excellent IQ, ideal for models with more background (some say it's no portrait lens cause -85mm lenses have distortion), but if you check the lens database it's actually perfect. Only 85mm would be too close and 24LII is too wide for portraits. And I can't use the Sigma 30 1.4 as i'm on FF, so 35 1.4L is perfect for modelling with more background. Zeis is probably better but I prefer AF.
16-35L II : ideal wide-angle zoom / urbex-lens, I first had version I but not sharp in the corners.
I also thought of the best price/quality 17-40 f4, but sometimes I don't like to work with tripod and urbex is often in dark environments, so the f2.8 II is Canon's best.
The new expensive 8-15 f4 is more a speciality fun lens. So I don't see any other fast competitor, also not from the alternative brands.