I have to say that I'm hooked on the App Store. The biggest reason? It's oh so easy to add the same apps on both my iMac and my MacBook. Buy it on one, and it will show up in the list of purchases on the other and tell me whether or not I've installed it. It's easy to see, in this screen capture, items purchased on my iMac that still need to be installed on my MacBook.
Want to know at a glance if any downloaded apps need to be updated? A quick glance at the Updates icon shows how many apps have updates waiting.
What's missing from the App Store? Try before you buy. If you see something that looks good, but you're not quite sure, don't buy it. Go to the associated website first and see if you can download a demo version. Check the price there, too. It might be different.