Check out what Panic had to say on the subject: http://www.panic.com/blog/2011/01/panic-on-the-mac-app-store...

I'm extremely skeptical about the long-term viability of the app store model, just as I was about trying to build on top of other people's platforms (Twitter, Facebook). But, that doesn't mean it can't work for you for a while, and if a company like Panic thinks that they should be in the app store, then that's probably worth considering.