One of the great things in TextMate 1 was that the Find/Replace dialog had a toggle to switch between the default view and an expanded view, where both text boxes were large scrollable "text areas", i.e. they allowed intuitive multiline editing of search-replace clauses. This is also how it's currently done in BBEdit.
The TextMate 2 Find/Replace dialog looks like the default view of TM1, i.e. consists of two "input areas", i.e. one-line controls. It took me a while to figure out that you can actually type Alt+Enter there, and then the controls expand vertically -- so it's better than the default TM1 mode.
But I still lack the truly "expanded" view where the text boxes were, say, 8 lines tall.
Also an important feature request would be the ability to "Show Invisibles" in the Find/Replace window. Actually, I think "Show invisibles" should be the default or even the only display mode in the Find/Replace text boxes.
Regards, Adam Twardoch TextMate user since 2007 (i.e. since moving from Windows to the Mac)