How do I know a refurbished laptop is going to be good.
It has the same return policy and warranty as a new Apple laptop. You can buy an AppleCare extended warranty on it just like a new laptop. It will actually most likely have gotten a more thorough inspection and quality checks than a new laptop.
Most people on this forum highly recommend them, they're usually indistinguishable from a new machine and if it isn't you can send it back. I bought my 2008 model refurbished and it was just the same as buying new except it comes in a different box.
You can also now choose to have it shipped to your local Apple store so you can pick it up there. That might be a good idea so that you can take it out of the box and boot it up in the store to make sure everything's ok.