White Industries:
The gear ratios are significantly changed when switching from one combination to another, however, the chain length does not need to be altered to accommodate the two differing ratios
I don't believe this. I ran a dingle for a while and the change in the angle of the chain between ratios means simply adding/subtracting 3 teeth does not mean you can keep the rr wheel in the same place.
I found it good as my staple rides were 50:50 on:off road. But i had to use a chainring as a tensioner, it was mucky and a faff, so I gave it in – road riding on 2:1 is good for the legs adn doesn't need to slow you down much.