After my previous post about IE7 being released i just wanted to add some more info about it. The tab interface is very much like the firefox with ctrl t opening new tabs and so on. One of the nice features is you can push a button which shinrks all windows and show you all open tabs in mini squares, a really nice overview feature to quickly switch between tabs visually.
Also like firefox there is a default search box, you can add search engines like modules from a microsoft site which is an xml based add in, which is nice that there is a standard, also on the page there is a form to create a custom search field. Which you can then pull into the I.E. search field.
Favourites, History and RSS are all handeled through the same sidebox which makes it a lot easier to navigate and use. It's a simplistic interface with a lot of the firefox features and a whole host more. Worth giving it a shot i think, from a useability pov it's coming close to firefox and obviously the microsoft integration features are there.
Microsoft are obviously taking security on board and have integrated the standard blocking features from their search bar and have included an interface to a central phishing list to try to improve overall net security.

*Edit*

Further to Jamerios comments i'm running 8 tabs on both i.e. 7 and firefox (Firefox V2 RC3), but with the same windows open in each one i.e. is using 23Mb of ram while firefox is using 80