Grab the OS update now by running Software Update on your Mac. According to Apple, this update lets you:
"Discover Mac apps: Browse featured apps, top charts, and categories, or search for something specific. Read detailed app descriptions and user reviews, and flip through screen shots.
Buy and install: Easily purchase apps with your iTunes account. Apps install in one step and are quickly available from the Dock.
App updates: The Mac App Store keeps track of all your purchased apps and notifies you when free updates are available."
Thus begins our Mac App Store coverage. Stay tuned to TUAW all day for in-depth analysis and exploration.