While I understand wanting applications to adhere to the Unix Philosophy, it seems to me that inputting and outputting text is what a terminal essentially does and copying & pasting is just a small extension of that role. I'd like to see a sane way of copying & pasting with the keyboard, rather than relying on the mouse for that.
Back on topic: The copying & pasting present currently seems to work fine for me, but I'd like to see a dynamic 'rubberband' over the selection - just to get feedback about what exactly is being highlighted while the mouse is still clicked. Programs like alsamixer work fine on my end - I'm not even noticing the slowdown that others are mentioning. (`time alsamixer` reports ~.01sec, which is exactly the same as I get on urxvt with my current Xdefaults.) I have noticed some problems with vim that I can't seem to fix with TERM, though. I need to do some more investigation into it.