Amazon's A9 search engine has gone out of beta stage into official release and now offers a lot more features.

This really is a major update so it's well worth checking out the website or downloading the toolbar to test all the new features.

The new features are:

• Lists - lets you to grab every link on a page or within a selection and navigate through them from the toolbar
• Online bookmarks - save your bookmarks to the a9 server where they are fully searchable
• Reference searches - from GuruNet, which integrates information from various sources into one "Answer Engine"
• Discover - a beta service that shows related sites, categories, frequently visited sites and movers & shakers. All seemingly data taken from the other Amazon search site, Alexa.
• Movie search from the IMDb
• Image search results from images.google.com
• Drag & Drop links for all results; very cool feature that works perfectly in IE and Firefox
• New skins & text size adjust

John Battelle had a first look at it and posted up a good review here.

The review calls attention to the main feature of A9, the clickstream, where your path from wanting to find something, to finding it, to where you go from there, are all recorded into a searchable History you can come back to anytime in the future.

As the review says, this could lead to a whole new way people search, but it would take time for it to be effective.
I've been using A9 on and off since the beta was launched in April, and my IE browsing history has been recorded since then so I can get an idea of its usefulness; but I don't know how many people would give it that much time.

I'm also not sure how willing most people would be to sign up to use all the bells & whistles, when Google is satisfactory as a search engine for most people.

Having said that, I have noticed demand on a few different sites for extras that Google don't offer - like thumbnail images in the results and a searchable browser history, both provided by tools like MoreGoogle and the Recall Toolbar.

A9 offers both of these + Google results + a lot extra, all in one free sign up, so if the major marketing push Amazon are planning convinces people to try A9, these extras may make them stick with it.

More info:
· A9.com Launches New Web Site To Make Internet Search More Effective - Official press release
· generic.a9.com - Bare-bones A9, an address to privacy concerns with logging the browser history
· Watch Out Google! Amazon Gets Search
· A9 Launches New Version - Discussion on John Battelle's Searchblog
· Gurunet.com - The source for the reference search in A9