But, by the way you asked that, you probably already knew that. Unless your computer is physically secure, in a room with multiple locks and no windows and there is always someone there carrying a firearm, I think you can imagine what will happen if someone broke into your home and stole your computer. I'm assuming that when you power up the machine, there is no login request for a user and password either.
It all boils down to how safe you really think you are and what you can afford to lose. Banks generally have some guarantee with their online service that, if you report a security issue right away, they will replace the money you have lost after an investigation. Credit Cards also have some limits as to what you can lose. The big issue would be Identity Theft. If you have enough information on your PC that someone can start opening bank accounts and get credit cards using your name, your social security number, your address and your telephone number, it could take a couple of years out of your life trying to piece your identity back together; not to mention your credit rating.
I've suggested this before. Either you or one of your friends should use your computer to see what damage can be done by getting into your account. At one point, I found that they could only move money from one account to another. But they there is bill pay and money transfers (on my bank, even to a foreign country). While the bank may send you an email to confirm, if your computer is gone and you have no easy way to check your email, whoever steals your computer can do a LOT if they can also access your email account.
There is always a teeter-totter effect with security on one side and ease-of-use/convenience on the other side. However, you really should NOT think of this as a "balancing act". You need to push down really hard on the security side of things as suddenly, your life will become VERY inconvenient if someone gets a hold of the information and cleans out your accounts and steals your identity.
What should you do? There are various password vaults out there. How good are they? How crackable are they? The answer varies. But think about this. If I were going to steal a car from the parking lot and all the cars were locked and alarmed except for one really nice one, guess which one I'd pick? Yes, the bait car! hehe
Really. Why would you need to ask this question if it doesn't take rocket science to figure out what would happen if someone broke into your home and stole your PC? Or if it was a laptop and you left it in a store or your iPhone in a cab. And you had all of the passwords right there..
So, if you think having your passwords right there and it will save you time, just remember. If the "unthinkable" happens you will be doing time. About 2 years of your life trying to straighten out the mess and get your identity back. Money would be the least of your worries.