I'm not an expert or anything, but my friends and acquaintances who do film professionally tell me that fast lenses are largely desired there not for thin DOF (think about it: you don't want 3cm DOF when a face is showing *any* movement at all). Rather, it's for the additional possibilities with lighting. Realistic environmental lighting, doing certain kinds of shots without setting the actors on fire with the arclights. Etc. Shallow DOF is the goal now and then for a certain shot but they talk about it more often as a (not really desired) side effect.
That's right. The truth is most portraits require apertures around f/4... Some lenses have a lot less than 3cm DOF even if they are not ultrafast lenses... My Leica 90 Summicron wide open at f/2 and focused close, has very few milimeters of DOF, (I checked it on print after shooting a ruler) not even enough for both eyes on focus, so that makes those conditions usable and optimal for a small amount of photographs only...
A strange thing about bokeh is how easily people tend to generalize a lens has bad bokeh... There are situations, depending on scene, light, focus and lens design, in which lenses can show different levels of softness on OOF zones rendering, and some people point at those situations, show them on internet, and all the sheeps get educated in the most amazing and unreal ways... Lenses are unfairly tagged and people sell them or stop buying great lenses in the most absurd ways... The most recent case I remember is the nonsense around the Nokton 50 1.1, an amazing lens from any point of view... But it happens with older lenses too...
Here's an image I showed on another thread a few days ago after being asked for an Ektar example... Nikkor 50 Ai wide open at f/1.4:
http://www.flickr.com/photos/40894234@N07/4908796616/
I've read lots of times "all Nikon 50 1.4 lenses show horrible bokeh"... Then you go and find the reason: a bad photographer not knowing about lenses or composition showed a photograph on a forum: close focusing on the shadows, and a background of leaves and branches under harsh direct sun, a weak and underexposed subject, no compositional skills and disturbing objects, etc., so all that person was able to say after looking at such waste of film was: "I should sell this lens and get another one with better bokeh..."
Bokeh is overrated and self perception underrated.
Cheers,
Juan