Sorry, I missed that this was a really old and already resolved comment, please delete or ignore my message
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I own a 3.5E and would never swap it for any F, 3.5 or 2.8, because the really important feature to me is the exposure lock. I learned how to operate medium format cameras with a Hasselblad and I started to think and work in EVs at that time, so any medium format waist level finder camera must offer the option of setting exposure based on an EV scale and it must be able to lock it for me to be really happy with it.
Could I do without? Of course. But I love and use the function much more than any of the newer features an F might offer. I have to say though that the screen was terrible and has been replaced by a Maxwell screen when I had it serviced by Harry Fleenor some years ago during lengthy construction job in the USA.
I would be interested in a 2.8E, but the additional weight and the high price tag keep me from it, since I honestly do not think that it will offer that much benefits over my 3.5E (Xenotar, btw)