I just found something of minor concern. I had a long line in my clipboard and pasted it by accident. Well with mirc 7 it split that line into 4 separate lines when it sent it to the chan.
So it'd be nice if there was an option like the current warning for pasting multiple lines. Because I just made a long line and it split to 8 messages, which I could see as a problem.
I think having it check how many lines a single pasted line would be split to and if it's over the "Confirm when pasting X or more lines of text" option warn the user.
While I can see this being handy, if it was introduced I would also like to see an option to turn off the warning message, that way if you send long lines on a regular basis, you won't get that warning message each and every time.
My favourite way to deal with multi-line pastes (including long lines that get split) is to enable the automatic multi-line editbox option (Options : Display : Options : Editbox lines = Automatic). (Multiple also works, but yields a continuously two-line tall editbox which is a bit annoying.)
The result is that multi-line and long-line pastes fill the editbox, without being sent.