When emacsclient is launched with -t (terminal mode), there is a short time when I press keys and they have no effect. Most commonly this happens when I open a file knowing that I want to search for something, so I immediately type backslash (bound to evil-search-forward), then the text I want to search for. When the slash and potentially some of the search term are eaten, strange things happen when emacs suddenly starts interpreting the middle of this key sequence as the start of it.
This doesn't happen when emacs is started normally in a terminal. One of my favorite things about using a terminal is that I can type ahead when I know what I'm doing, and I don't have to wait for the GUI to catch up to me. Emacsclient breaks this, and it is especially noticeable over ssh. I have confirmed that this happens with no init file, so I'm sure it's not just something in my configuration.
Confirmed in emacs versions 24.5.50.1 and 25.0.50.1.