I love the App Store, it's similar to the iTunes App store, if you were to cut that out of iTunes and make it it's own program.
I find the main page of it a little sluggish though, but once you click on an app description or get the list of Top Paid or Top Free, its smooth.
I made a folder for all my downloads from there to keep track. It puts them on the dock and a copy in Applications. I took them off of the dock and have them in that folder. When it updated Angry Birds, it didn't reposition it in the dock again, which was nice, it updated it where I moved. Of course in Windows, that could never have happened, haha.
I also wish the App descriptions had requirements. Just putting Mac OSX 10.6.6 isn't really enough for some of the more demanding programs.