An OS X App Store would be nice without the app approval. But yes, the idea of having a centralized store for Mac applications would be nice.
As long as:
1) you can use more stores than just the Apple Mac OS X App Store (3rd party stores),
2) you can continue to "sideload" (ie. standard "install on your own") apps
then I'd be VERY in favor of a Mac App store. But, as someone else already pointed out, that SORT OF already exists. It would just need to be re-vamped and marketed better.