PDF editing hasn't changed, it's just that some PDFs have text fields while others don't. It's also possible that Preview isn't compatible with all PDFs' text fields, idk. That "text" button was always there as a fallback.
Oh ok. I'm not sure about the undo thing, but the behavior of a placeholder "text" box appearing in a random spot has always annoyed me, and it's felt hard to resize. That's not new.
Semi new thing is the removal of proper "save as" in Preview and other 1P apps starting in Lion. Still sucks and still hasn't caught on in 3P apps.
