You can get it from here, and read about in the IE blog.
N.B. This is intended for developers, although unlike beta 1 it's available to everyone (rather than just MSDN subscribers or people who found a dodgy copy on the web). So, for the non-techie people reading this (e.g. princesslen and elyon), I'd recommend that you stick with what you've got, rather than playing with this.
This release only works on Windows XP SP2, and it replaces the IE6 installation, i.e. you can't run them side by side. That's probably not an issue if you use Firefox as your main browser, but it's something to be aware of (e.g. you can't flick back and forth to compare how pages look in the different browsers, unless you use something like Virtual PC).
Anyway, I've installed it, and so far I'm not hugely impressed; it's already crashed on me once, due to the "IEFrame" extension. It could definitely do with some more tooltips, e.g. I thought that the "search" button was actually a zoom button (magnifying glass), until I clicked the drop-down arrow next to it. Similarly, when I viewed my LJ friends page, I got a warning icon in the status bar, which turned out to be because of restricted cookies from the moblog website (in billyabbott's post), but I only found out the details by double clicking on it.
Speaking of LJ, that website seems to have the most problems so far. When I initially loaded my friends page, none of the images showed up, but the status bar said "Done". When I went to a different window and came back, the images were all there. Now that I've played with it a bit more, there seem to be some related issues where everything is fine until I scroll up and down, at which point pictures either disappear or get completely misaligned. (The padlock icon for locked posts is a prime example of this.) This could be because the LJ website isn't producing validated HTML, or it could be an IE bug, I'm not sure which.
Outlook Web Access seems ok, although it keeps giving me vague security warnings, without any obvious way to say "this is a trusted website". (I think this is the equivalent of the old "this page contains a mixture of secure and unsecure content - do you want to view the unsecure items?" message, which was always a bit pointless since it wouldn't warn you about a page which only contained unsecure items.)
Edit: Oh, and I get pop-up warnings now, despite the fact that my webserver is already listed in the "allow pop-ups from these sites" list - either that's broken, or it doesn't accept wildcards anymore.
It won't load up my XML pages in the errata section of my website, which is rather annoying. I need to update the compatibility page there when I do my next overhaul, but for now it looks like Firefox 1.5 is the best browser for XHTML/MathML/SVG; I need to check my site logs to see which browsers most visitors are using before I shift over any more of my maths pages to use MathML.
The tabs are nice, although it will take me a while to break the habit of using Alt-Tab to flick between windows, and I haven't found out what the corresponding keyboard shortcut is yet (Ctrl-Tab and Shift-Tab don't do anything).
The RSS feed support is also handy, although I haven't quite figured out how it works yet (documentation is rather minimal) - so far I've been able to set up a list of favourites in my "Feeds" folder, which basically mirrors my existing "Blogs" folder, but I don't see any obvious way to go to one page (like the LJ friends list) that will say "here are the latest posts from all the RSS feeds that you subscribe to".
Edit: I assume that the feeds which appear in bold are the ones with new entries, but it still means going to each one in turn.
Incidentally, I'm not trying to start up any arguments here about the relative merits of Firefox and IE (or any other browsers for that matter) - I'm just looking at IE in isolation.
Anyway, I'll stick with the new version for now, and submit info to Microsoft, so hopefully things will improve before the final release.