This tidbit caught my attention, and I realized that I had never tried playing mine with the button in - (So a G harmonica, button in becomes Ab, so playing in 2nd position in the key of Eb.) So I went and tried it…3 HOURS LATER, I was so jazzed that I had trouble falling asleep that night!
(I also read through your book Peter!! 
- and I highly recommend it to anyone who’d like an academic explanation of the GameChanger harmonicas. I’m sure I’ll be returning to it from time to time in the future!)
For players who play a fair amount of chromatic, playing with the slide in may just be old hat, but for me, playing with the slide it was a…well, a game changer! 
Why? To use some jazz theory jargon: In my experience, when improvising, I use lower chromatic approach tones a lot more often than upper chromatic approach tones. They just sound more musical more often.
I’ll have to make a little video some time. But my Game Changers were starting to gather dust, and now they are out and getting a lot of love again! AND, I’m considering buying a couple more keys!!!
Thanks @Hogie.Harmonica