It's flexible but it's dangerous.. the temptation to just pay the interest and have the money you'd normally go towards the principle get eaten up in living expenses would be too great for a lot of people to resist.
It's also a variable rate on the LoC and that rate is a bit higher than what you can usually find for shorter term variable rate mortgages, so the investments and tax advantages have to make up for that. In the simulations I did there was actually a disadvantage in the first few years assuming reasonable returns on the investment, but after 6-7 years it really starts to kick in.
I never do want to pay off my mortgage, I just want to be able to borrow against the equity so I can invest. This lets me do that while still benefiting from the growth of the property value.
Debt is good as long as it's for assets that provide a greater return than the cost of borrowing
