I remember posting when the Sony 35mm f2.8 came out that f2.8 was just enough and for a lot of things it is but you wont get those bokeh balls without working for them. f2.5 isn't a whole lot better and some would miss the difference between 1.8/2 and f2.5/f2.8.
Ignoring light for a moment and just looking at depth and bokeh. For me obvious difference between F1.2 and smaller apertures kick in at about f2.2 or so. By f2.5/f2.8 the differences will be quite obvious.
Just out of interest. The difference between f1.2 and f1.4 for DoF and bokeh has cropped up a couple of times so I thought I'd post a series of pictures. Note that I'm ignoring light gathering here and just looking at depth of field and bokeh. I looked at bokeh and depth of field years ago and...
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I hope I'm wrong but I just can't see anyone bringing out a mini G sized 35 or 40mm f2. I don't think companies will be willing to make the compromises. For me my Voigtlander 35mm f1.4 gives acceptable performance at f2 with wider apertures being available for suitable scenes when the funkiness will be less noticeable and also for emergency use. I'd love a compact if less than stellar 35mm f2.