Expansion of Add Remove Programs - show user-provided descriptions, feature lists, screenshots, comments, ratings, integration with launchpad. Initial page should be top-rated apps, or newest apps. Managed by a webapp?
Or... leave it as it is, but create a website displaying all the great software available for ubuntu including all the features mentioned above with apturl links to install.
From #4613 (merged):
It should be indicated how much I'll have to download to install something.
We have download limits here and well... quite often I exceed them. It would be useful to indicate how big the download is going to be.