It's based on the WebKit rendering engine (same engine used by Safari and iPhone browsers). It's a later version of WebKit since it gets further in the ACID 3 test (97/100) than the release versions of those browsers, and much further than any other Windows Mobile browser. So it's a good choice for those heavy CSS/Javascript web pages.
For the full feature list visit this page:
http://www.torchmobile.com/products/iris.html
Here's a video of it in action on Windows Mobile:
http://www.youtube.com/watch?v=KpX5JZWtu-g
Here are my observations:
Pros:
- Free
- Fairly fast
- Very standards compliant (97/100) on Acid 3 tests
- Native support for Touch Pro/Diamond accelerometers (goes to landscape when you twist your phone sideways)
- Direct, doesn't go through a proxy like Opera Mini or Skyfire (which is good if you're paranoid about security/proxy availiblity)
- Tabs
- Can simulate a mouse cursor in "Mouse Cursor" mode
- Downloading support, though did silently crash once when trying to download Google Maps cab
Cons:- No flash support (though flash mostly sucks in Opera MObile/IE anyways, if you need Flash use Skyfire)
- No text reflow/reformat on zoom-in like Opera Mini and certain versions of Opera Mobile 9.5
- Extremely basic UI, every function has to be accesed through menus which gets kind of clunky
- Zooming is clunky, zooming in more than one level/accessing the URL bar requires you to go through the menu system
Tip: Tap and hold link to go to visit links and give focus to certain form fields (checkboxes/textboxes).