Do you keep your client informed of progress?

A client will always prefer to be told ahead of time if a piece of functionality is going to take longer than anticipated. It gives them more control of what is going on. The other opinion is landing them with an oversized invoice with no warning.

For this reason, blowouts should be reported in the Daily Scrum, as well as any major delays being told to the client as soon as possible, so that they don't get a big surpirse in the Sprint Review.

For big delays, it's best to tell the client as soon as the risk is identified to inform them of what's going on and ask "Do you want us to continue?".