What would you do to improve an e-commerce site like Amazon?

Need To Do  Daily Research on Your Customers Searches, Keywords,Requirements . And Need to keep The Kite eyes on Your Competitors with Very positive Approach . And Ya a talented Team of SEO's Makes this task more easier. Hope you will Agree. Thanks  

Need To Do  Daily Research on Your Customers Searches, Keywords,Requirements . And Need to keep The Kite eyes on Your Competitors with Very positive Approach .

Daily data gathering.

Make it user-friendly.

Use a relaxed color theme.

Include most attractive offers.

increase the loading speed of the page.

uwak! :P I don't like amazon,

Its quite a broad area question, you need to be more specific.

Are you looking at consolidation of categories, filters per category, cart handling, checkout process, user experience, the UI itself, the backend handling, notifications  etc ?