Ok, the only thing I've found to be a bit slow and unneccessary is, when you switch between the shooting modes via the P, Av, Tv, M dial. I have turned off tips&tricks in the menu, but everytime I switch, it shows me the mode I've just selected on the display for about 1sec. (or even longer, didn't measure) and I cannot do anything in the meantime! I don't need that. Annoying stuff (but I can deal with it, as I'm more into landscapes).
Now but if I'm in a hurry, that might be an issue (street photography, weddings, festivals, frequently changing situations, etc...). It might take a splitsecond too long to finally be able to shoot, after I've switched from Av to Tv mode for example. Should be fixed in a firmware upgrade for the Canon EOS M5.
P.S.: One thing I want to add about the in-camera RAW processing; the M5 allows you to select and then process multiple pictures at once (you couldn't do that with the 6D).