I can report that at least for preview 5 of 4.11 Distance field shadows do work for stereo rendering… kinda.
Firstly for my setup running a 970 the average cost to update the global df for MY PARTICULAR SCENE is around ~5ms for both eyes combined as I have quite a few dynamic objects in the scene(could it be optimized so that it is done only once and shared for the second eye I am definitely not capable of saying). This could be close to 0ms if you have little to no movable dynamic objects.
Secondly my use case for this is not regular indoor lighting and I can see some artifacting further away form the lights in the form of big black squares(not visible for regular rendering, but they are more evident for movable objects), so this might not affect you, but be aware that you could run into this problem and when you do it is very nasty. I will play around with cvars a bit to see if that can fix it.
Thirdly, is the fact that rendering movable shadows (with softness which is basically free and AO on top) is actually cheaper this way if you have complex geometry (realtime shadows are generally still considered bad practice in VR I know).
The added cost of updating the global DF (not hitting 90fps) and artifacting I get with this makes it unusable for me at this time. Though in a blank project, where I tried it first I did get very exited thinking of the possibilities as I actually did reach the performance as there were no dynamic objects there and I could enable both DF shadows and AO. So this might be something to check out as it might just work for you 