Cheng Chuan in his talk had a slide about what not to pay for using CPF but there wasn't enough time. Could he elaborate a bit more about that?

It's pretty much everything. Don't use your CPF to pay for anything.

Not housing loans, not student loans, nothing. Because you'll have to pay it back with accrued interest.

Theoretically, if you can hold out until 55 and pay the rest in cash, you should have far more guaranteed, liquid money than you gave up. Especially if you transfer from your OA to your SA. You'll have 4% risk free, on top of any 1% bonus here and there up to 6%.

The concept is generally delayed gratification, not unlike any other investment. But it assumes that CPF stays constant (highly unlikely, but...).