Type of Engine: Meta-search.
Overall: Very good.
If this engine were a drink it would be…a martini. It’s not so much about the complexity of the mixture, but it’s always classy and it gets the job done.

A9 has implemented some really clever UI features. At present they’re searching Google’s Index for web searches, but seeing as how they’re owned by Amazon I expect bigger things from them in the future. Because they’re using Google I won’t go into relevancy. The UI is the first thing you’ll see and it’s what sets them apart, especially since right now they’re using the Google Index and (I think) the Google algorithm with some slight tweaks. The number of results sometimes varies, though page 1 results on A9 and on Google seem identical.

UI and Features
You can focus your search in the following ways:
Web – searches Google
Books – searches Amazon
Images – searches Google
Movies – searches IMDB
Reference – searches GuruNet

Some nice things worth pointing out
• The UI – the tabs are very easy and load right away so that you don’t have to wait for a new page to load.
• Amazon Discount – If you search on A9 and then go to Amazon.com to buy something, they’ll cookie you and give you a 1.57% discount on purchases. I pleasantly discovered this since they don’t seem to advertise it.
• Search History – They maintain a list of your search history that you see right away when you visit A9. I didn’t think this was the most useful feature at first, particularly now that browsers save searches, but I’ve actually used it to recall previous searches.
• Diary – this function lets you leave notes about sites (I use Mozilla and you need IE so I haven’t been able to do this yet, but it sounds cool).
• Bookmarks – they have a built in web-based bookmark function. Personally I don’t see why this is better than using my browser, but that’s because I don’t spend much time on public or shared terminals. For people who use different computers this is a valuable feature.
• Discover– similar, I think, to Amazon’s “You’ve bought this, so check these out,” but with web sites instead of products.
• Preferences – you can set language default, filtering level, font size and colors. I’m guessing they’re still working on adding advanced features here but they may be limited by searching Google’s index for general web results. Just a guess.

A9 is part of my regular repertoire. I’m hoping they build their own web index and algorithm, then they’ll vault into the elite ranks of search engines. If that doesn’t happen they’ve still got one of the finest UIs out there.