Personally I like to play games as they're intended back in the day (save states, cheats, etc, aren't my cup of tea). One interesting point I'd like to make is that some NES games were actually designed with turbo controllers in mind. Now, the vast majority I'd say it's a no-go if you're a purist, but what about these "Turbo Approved" games?
Thundercade (NES, 1988), in the hints section of the manual (page 13), it states:
" * Using a joystick with rapid-fire will improve your fire-power. "
http://www.thegameisafootarcade.com/wp-content/uploads/2017/03/Thundercade-Game-Manual.pdf
Abadox (NES, 1989), page 5 of the manual states:
" If you have any NES controller which has the "turbo" feature, hold down
the turbo button for steady bursts of fire power rather than just single
shots. "
http://www.thegameisafootarcade.com/wp-content/uploads/2017/02/Abadox-Game-Manual.pdf
With that said, I personally don't use turbo when I play; I think the rabid button mashing adds to the intensity/experience, despite the side-effect of major Nintenditus. Ha.