It would have to be a mighty quick expression to miss it. The speed of the EVF is a non-issue to me. Auto-focus speed could be more of a problem, especially in low light.. That being said, only you can judge whether you will be happy with it. Try it and see if it is quick enough for your needs.
Fuji X-E1 w/ 35mm f/1.4 and 18mm f/2.0www
Canon 5D MkII w/ 24-70 f/2.8, Sigma 50 f/1.4, Canon 85 f/1.8, etc, etc...