[jammycakes]

That's a good approach if you can cleanly separate out the old code from the new code, and if you can make sure that you've got all the old functionality behind the switch. Unfortunately this can be difficult at times. Feature toggles involving UI elements, third party services or legacy code can be difficult to test automatically, for example. Another risk is accidental exposure: if a feature toggle gets switched on prematurely for whatever reason, you'll end up with broken code in production.

The cases where I've experienced problems with feature toggles have been where we thought we were swapping out all the functionality but it later turned out that due to some subtleties or nuances with the system that we weren't familiar with, we had overlooked something or other.

Feature toggles sound like a less painful way of managing changes, but you really need to have a disciplined team, a well architected codebase, comprehensive test coverage and a solid switching infrastructure to avoid getting into trouble with them. My personal recommendation is to ask the question, "What would be the damage that would happen if this feature were switched on prematurely?" and if it's not a risk you're prepared to take, that's when to move to a separate branch.