How abrupt would an '06 800 feel compared to an '08 or a '14? One of each of those is available in my market. For reference, I put 5k miles on a '86 VFR 700. Also I put and 50k miles on a Shadow 600, 25k miles on a BMW K100RT, 12k miles (and rising) on a V-Strom 650. Not sure how trustworthy it is, other than general reference, but attached is a rear wheel, measured Hp vs RPM set of curves ChatGPT generated for me.
I bought an 09 last year and IMHO the VTEC transition is smooth enough, you know when it is happening but it is not upsetting in any way, and just adds a bit of character. The 14 is said to be better again and when I test rode one (probably in 2015) I can't recall the transition at all but maybe I didn't rev out that far.