If the $mouse now is set to work with items in a dialog, that's great.
However, regarding $inrect... *YOU* specify the rectangle used, so *YES*, you can use $mouse and $inrect without any problems.
Yes, now that $mouse will do it for you, it's great. But, that way will work just fine and is really not too much of a pain to code if you're making a script that can be used on older versions of mirc that do not support the new $mouse ability.
If you don't believe me, I suppose I could write a sample script. Let me know if you need me to show you how it works. Again, that's for anyone who wants to run their scripts on older mircs (which some people do like having backward compatibility).