Whether they loved it or hated it, all reviewers of the iPad agreed that usability of "normal" PCs for average users is atrocious. And I have to agree: whenever I take a look at the PC of a friend or relative who is not a "computer freak", they are always riddled with spyware and malware or at least ladden with useless software that draws away time and energy of the user (examples are "Toolbars" like the Google Toolbar or the Yahoo Toolbar). This is not only because they might have downloaded or installed bad software from questionable sources, but because even vendors or seemingly trustworthy businesses have no qualms to sell their customers. Usually a new PC is already messed up by the software the vendor has preinstalled. If not that, then the new gadget (camera, navigation system, whatever) might come with crappy software.
But I don't want to rant about the various ways today's PC software and hardware vendors mess up the PC experience. The point is, by many reviewers the iPad has been hailed as the savior from this hell of malware and overly complicated software. What I want to mention is that the "geeks" (computer savvy people) have actually been aware of this problem for a long time, and they have invented a solution long before Apple's App Store. It is called APT.
APT is a front end to the package managers of some Linux distributions, most notably Debian and it's derivative Ubuntu. By using it you can install software from a trusted repository of open source applications (trusted because it is open to peer review). It is not the only way to install software on these Linux systems, but usually if you opt to install software from another source, you end up feeling slightly icky and dirty, as you should.
To avoid icky spyware, malware and so on, just stick to the official repositories of your Linux distribution. It is as simple as that - no debilitating iPad required.
Now I have to go ahead and admit that I am not even that well versed with Linux and apt. I know how to find, install and remove programs, and some other internals that are not really important. But isn't that kind of the point: you can use Linux and apt even if you are NOT a "computer freak". There are simple front ends that enable you to use it without using the command line. The main difference to Apple's App Store is that it is still open - using apt is entirely optional, but recommended.
Of course, things on Linux don't always run as smoothly as with a Mac (although I have whole lot of things to complain about with Macs, too). Not all the software in the repositories is very polished or even bug free. But neither is software in the app store.
As for stability, it helps to look at the hardware Apple has on offer: presumably they only actually sell three or four different kinds of computers (a laptop, which includes the iMac and the Mac Mini which are also based on laptop internals, the Mac Pro, and the iPhone/iPad). Most Linux distributions try to support a far wider range of hardware and therefore are less optimized for any specific piece of hardware. But it would be possible even today to launch computers with a Linux distribution optimized just for these computers. They should have no troubles achieving adequate stability.
Anyway, maybe you get the idea, maybe you don't, all I want to say is this: the App store model is NOT our only salvation.