The numpad seems to be the decision point here. Before moving to TKL about three years ago, I relied on my full sized keyboard numpad for all number entry. I never used the top row numbers. I was a touch typist that never learned to touch type numbers. But I had a copy of Mavis Beacon Teaches Typing, and in it she had number only drills. So over the course of about a week, I learned to use my top row numbers rather than always reach for the numpad. Now, I only use my numpad if I'm doing dedicated spreadsheet data entry. Everything else, I use the top number row. Phone numbers, zip codes, even QuickBooks accounting entries are all done from top row numbers. And since my hands remain on home row, typing numbers with text is seamless. Much faster than reaching for the numpad when a few numbers are required.
When I need a dedicated numpad, I just pull it down beside my keyboard as in the picture. It lives right above my right mouse pad. For me, the added ergonomics of having my right mouse closer with a TKL board far outweighs the benefit of having a numpad taking up valuable work space real estate when I don't need it. When I do need it, it's always right there.
I am willing to bet those who insist on a full sized keyboard can't / don't touch type top row numbers. If that's the case, do yourself a favor and learn to use those numbers. You'll be glad you did.
