And although many on Slashdot complain about the "Walled Garden", having an App store run by Apple itself provides some assurance to the customer that the App is legit and not some form of malware.
I don't think malware is particularly worrisome in the average user's mind. I think it's more about quality.
Speaking as an application developer, the vast majority of times I've had to say to clients "Apple won't allow that", it's been something that is self-serving and user-unfriendly if not downright abusive. Apple serve as a convenient foil for developers who care about users and stop developers who don't care from going too far.
As a developer, I know first hand how frustrating it is to have a great idea for something that Apple simply won't allow, but at the same time, I frequently see the benefit its policies bring to end users.
For instance, just the other day I saw a developer complain that a client wanted to force users to enter their personal information (e.g. age) before they could use the application, so that they could use it for marketing. Simple solution: Apple don't allow that. But Google does. How do you think policies like that are reflected in the average application quality?