I was a Mac user for 17 years, and when I finally switched over to PC keyboards, I did miss the feeling of those two firm, upright nipples poking at my middle fingers. The underscores on F and J, which I couldn't even feel unless I massaged the keys with my index fingers, seemed wimpy and ineffectual to me. However, I must note that I did not touch-type at the time. I only learned to do so a few years after graduating from Mac to Linux.
If I had been a touch typist during my Mac days, I might have found the D and K nipples somewhat inconvenient. Or maybe the middle-finger nipples would actually be better for touch typing than the index-finger underscores. I just don't know. All I know for sure is that I still miss the sensation of those nipples. Then again, I also miss the
512 x 342 monochrome CRT of the original Macintosh, and I probably wouldn't be more productive on such a screen today than I am with my 1920 x 1200 color LCD.