Whilst I'm not planning on selling anything through the App Store myself, I agree that we need to be able to buy and sell software more easily for Linux.
There is this nasty perception that Linux users don't - or worse, won't - buy software. And I think that's complete crap.
It's no doubt caused by a very vocal minority of people that genuinely won't buy software. But most users will happily pay a reasonable price for well-written software if they need or want it.
It's not helped by the fact that some of the attempts to sell software on Linux have been a bit naive - going after the FPS gaming market, for example. That just seemed premature.
Myself, I've bought software for Linux when I couldn't find an acceptable open source solution. So far, off the top of my head, that means I've bought VMware Professional (at the time VirtualBox's USB support was ropey), Bibble Pro (versions 4 and 5), LightZone, and others.
Some software projects just aren't really feasible for free software without significant support (i.e. Sun supporting VirtualBox) or a commercial revenue stream (i.e. Bibble Labs sometimes needs to buy new cameras to properly profile them). Hopefully, the community can recognise this and make it easier to be successful on the Linux platform.
In an ideal world, maybe we could also get a "Donate" button so that some GPL'd projects can do better too. I really like the idea of being able to install something and then donate to the project via the same software centre... Maybe a "recently installed" view which shows a Donate/Give Thanks button for projects that choose to participate?
Hmmm. Time to hit the Launchpad for the Software Centre and throw in a suggestion or two! :-)