
My initial impression about this browser is that it's very much like
IE. Loading up my website I notice that dashed borders (as you see in the side bar on the right) show up exactly as they would in IE7, and many of IE's quirks seem to follow. As I write this, the scroll bar in the small box does not work properly for IE, and it does not work in Avant in the same way.
edit: Upon further research... I happened across
this bit of information:
Avant Browser enhances your copy of Internet Explorer, even if you've upgraded to IE7, with ad-blocking and other handy features.
Back when Internet Explorer was languishing without a major update, a few enterprising developers figured out how to build a tabbed interface and other missing amenties around IE's basic web-page engine. One of those products, Avant Browser, was a boon to IE 6 users, adding much-needed tabbed browsing and newsfeed support.
Even today, the program still improves on IE 7 with ad blocking, a flash animation filter, mouse gestures, and skins. The program also lets you store your bookmarks, saved passwords, newsfeeds, and other configuration data online allowing you to synchronize your browsing experience among multiple locations.
The reason it looks so similar is because it basically
is IE with enhancements.

As for the
UI, it has some nice features.
The first thing that caught my eye while poking through the menus (which are oddly, but not annoyingly located on the upper right hand corner of the browser by default) was the abundance of preloaded skins.

The skins range from bland grayish themes to good enough grayish themes with a bit of color for menu selections. My eventual selection was AthenX. Although most of the selections are more or less the same with slight variation in color and texture, at least Avant gives you a choice.
Other tools I found interesting:
Built in auto-fill

This is something that is accomplished by the Google toolbar in other browsers, but Avant has one thing they don't. You can sign up for an account that will host your password information online so you can access it from any computer via a login.

I don't know how comfortable people are with sending all of their login information to where ever the online password storage is, but it certainly is convenient to keep things consistent between computers.
In addition to built in adblock, which comes with an extensive pre-populated black list consisting of sites such as doubleclick.com and adserver.com, as well as subdomains such as i.us.rmi.yahoo.com which are known advertising sources, there are other tools that users might find useful.
As in Firefox and Opera, this browser will also save your sessions if you like. Instead of just a dialogue at the beginning, you get one both when you close the browser and when it starts up. When you close the browser for the first time, you're asked to set a default: save all sessions, save no sessions, or ask upon closing. I select saving all my sessions, and restart the browser. This dialogue pops up:

This is a cool feature, letting me pick and choose what I want to load, rather than loading every Wikipedia page I was looking at and forgot to close in addition to the 2 or 3 pages I actually want to load. Takes less time than closing each window I didn't actually want.
There are other nice features, such as a well organized tools menu which takes a lot of the obscurely placed options and places them in a much more accessible place. (see skins image above) You can clear your records such as form data you've typed, and you can enable/disable all types of multimedia without hunting for the right tab in the options menu.
Probably my favorite new feature is in the toolbar: an undo closed tab/window button. While you can undo a closed tab in Firefox, you actually have to have at least 2 tabs open in order to do so... and it just so happens that more often than not, it's when I have 1 tab open that I need to reopen a tab that I just closed. This button streamlines the process nicely, a welcome feature.

Beyond those mentioned, there isn't a whole lot new and special about this browser. I miss the gestures built into Opera, and availible
via extension to Firefox. Avant only has forward and back gestures set like the other browsers, the rest would either have to be reset or relearned.
The benchmark of whether a browser is good or bad, the
webstandards.org Acid Test, is good for checking if web standards matter to the people writing the browser... and this browser fails that test miserably.
Here's a set of screenshots showing how all the browsers check out on the Acid 2 test:
This is what is supposed to be displayed.This is how browsers attempt to display it:Internet Explorer 7.0(What. Is. That.)
Firefox(Good enough... Firefox is quality)
Opera(Opera wins this round!)
Here's one just for kicks, as a means of revenge on the version of IE I hate so much:
Internet Explorer 6.0 (Hey! You can almost see a smile in that picture!)
There's the basic overview of the Avant Browser. I encourage you to check it out for yourself and leave a comment about good or bad things you find with the browser. I won't be switching to this browser as none of the features I like are key features, and the lack of standards compliance bothers me.
Stick with Opera or Firefox for the strength of the extension communities and quality of page rendering.
The Good: The interface
The Bad: Based on IE, lack of typical gesture motions. [Andrew, in the comment below, pointed out that gestures did exist, just with different motions than I'm used to. Since I was tempted to give a 2.5 due to using IE as the base, I'll leave the rating as a solid 3, rather than the previous tentative 3.]
Bottom Line: 3/5
Labels: Acid, Avant, Browser, Firefox, IE, Opera, Web Standards, Web Tools