If I attempt to alt tab while connecting to a server then upon entering I won't be able to use my pushtotalk button to chat and if I do try to use chat my backspace key won't delete a character from the buffer. After a map finishes and the server is switching maps I can alt tab freely.
How can you even alt tab while source is loading anything? For me (if its maximised anyway) its freezes everything barring a ctr-alt-del command
You can alt tab as soon as you hit the join button, but not really later than that. I do it all the time so I can change music before getting in server.
Just play in windowed fullscreen mode and you can alt-tab all you want in sourcegames. Just put this in the launch properties of Empires in the steam menu: -console -windowed -noborder