I understand the logic behind the "Th" ligature, of course, and I've tried my best to get used to it, but frankly, I can't stand it. Not only is it typographically unidiomatic (so that it always looks a little like a mistake -- and indeed, people often say, "something's wrong with your printer!" when they see it), but it's also just ugly. In the "f" ligatures, the f's curve flows neatly into the following letter, but the rectilinear collision of T and h doesn't create a natural join: it usually looks like they've just been tightly tracked to overlap. The net effect for me is oddly runic, and I'd rather not have it in the books I'm setting.
Moreover, it's a PITA to work around: you have to do a find and replace and deal with any reflow that arises, which pretty much necessitates doing the F&R on a case-by-case basis. In a 250-page book, that's a whole lot of clicking the Change/Find button.
How do you work around this? Or am I the only one who hates this ligature?